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, Yang, Kaidi, Menendez, Monica, Guler, S. Ilgin, 2016 >>
Author(s): Yang, Kaidi, Menendez, Monica, Guler, S. Ilgin
Title: Using Connected-Vehicle Technology to Optimize Transit Signal Priority
Abstract: Transit signal priority is a cost-effective way to improve transit operations and reliability. Connected vehicles provide more precise and detailed information on vehicle movements, thus can be beneficial to provide priority to public transportation. This paper proposes a transit signal priority algorithm using connected vehicle information. The algorithm can be adapted to situations without/with bus stops (both near-side and far-side). Moreover, it can minimize either signal delay or schedule delay for buses. Simulation is conducted for different volume to capacity ratios, bus arrivals, bus occupancies, and penetration rates. Results show that this algorithm successfully reduces the total passenger delay. It is also shown that this algorithm is not sensitive to the assumed bus passenger occupancy, hence does not require accurate information on bus occupancy. Overall, this algorithm seems rather promising as it significantly reduces the delay of buses with minimal increase to the delay of cars in the conflicting approach.2
Publication date / Date received: 2016-01-01
Event name: 95th Annual Meeting of the Transportation Research Board (TRB 2016)
Event date: 10-14 January 2016
Place: Washington D.C., USA
Language: English
DBID source: FORM-1454099918
, Nikias, Vasileios, Guler, S. Ilgin, Menendez, Monica, 2016 >>
Author(s): Nikias, Vasileios, Guler, S. Ilgin, Menendez, Monica
Title: Effects of bus operations on urban networks
Abstract: 2
Publication date / Date received: 2016-01-01
Event name: 95th Annual Meeting of the Transportation Research Board (TRB 2016)
Event date: 10-14 January 2016
Place: Washington D.C., USA
DBID source: FORM-1454010733
, Lüthy, Nico, Guler, S. Ilgin, Menendez, Monica, 2016 >>
Author(s): Lüthy, Nico, Guler, S. Ilgin, Menendez, Monica
Title: System wide effects of bus stops: bus bays vs. curbside bus stops
Abstract: The type and location of a bus stop located on an urban street can have a large influence on the delays imparted to private vehicles (i.e., cars) and also buses. Bus stops can be placed curbside or in a bus bay, and close or far from bottlenecks. At curbside stops, buses can block the cars behind them leading to additional car delays. On the other hand, buses that stop at bays can get delayed themselves since cars can block a bus leaving the bay. Additionally, when using bus bays, a bus can lose its position in the queue if the bus stop is close to a signalized intersection. This paper theoretically analyzes the delays that cars and buses experience based on the type and location of bus stops. Equations to determine the car and bus delays for a single lane road with a curbside bus stop or a bus bay, located either close or far from a bottleneck are developed. The goal is to determine the type and location of a bus stop that minimizes the system-wide delays (total passenger delay) for different vehicular and bus passenger demand values.2
Publication date / Date received: 2016-01-01
Event name: 95th Annual Meeting of the Transportation Research Board (TRB 2016)
Event date: 10-14 January 2016
Place: Washington D.C., USA
Language: English
DBID source: FORM-1454012099
, Guler, S. Ilgin, Gayah, Vikash V., Menendez, Monica, 2016 >>
Author(s): Guler, S. Ilgin, Gayah, Vikash V., Menendez, Monica
Title: Bus priority at signalized intersections with single-lane approaches: A novel pre-signal strategy
Abstract: Signalized intersections often represent a major source of bus delays in urban environments. One strategy to mitigate this problem is to dedicate an existing car lane for bus-use only and use an additional signal to help minimize interactions between cars and buses. However, this is physically impossible at approaches where only a single travel lane is available for each direction. To this end, this research explores a novel method to provide priority to buses at signalized intersections with single-lane approaches that (nearly) eliminates bus delays while minimizing the negative impacts imparted to cars. Using additional signals to stop cars on the opposing travel lane, the bus can jump a portion of the car queue using the travel lane in the opposite direction. This paper theoretically quantifies the delay savings buses can achieve, and the negative impacts imparted onto cars when this pre-signal strategy is applied. The negative impacts are measured as the additional car delays experienced when the intersection signal is under-saturated, and the reduction in car-discharge capacity when the intersection signal is over-saturated. In the under-saturated case, the results show that moderate average bus delay savings (~~5–7 s per vehicle, equivalent to about 25% of the average delay expected at the intersection) are achieved if the pre-signal is always in operation and the total passenger delay is decreased only if bus occupancies are very high. However, if the pre-signal operation is targeted to only provide priority to the buses that would benefit the most, bus delay savings can be more than doubled while reducing the total passenger delay, even if the ratio of bus to car occupancy is relatively modest (greater than about 20). In the over-saturated case, bus delay savings can be much more significant (greater than 30 s per bus), and this delay saving can increase further for longer block lengths (greater than 100 m). However, the capacity of the intersection decreases by up to 25% during each cycle in which a bus arrives to the intersection. Simulation tests confirmed that the general trends and magnitudes of bus delay savings and negative impacts to cars hold for more realistic behaviors. The overall benefits are slightly smaller in the simulations, but nevertheless the strategy seems promising as a bus priority strategy at intersections with single-lane approaches in the field.2
Published in: Transportation Research Part C: Emerging Technologies
Volume: 63
Pages: 51 - 70
Publication date / Date received: 2016-01-01
Publication status: Published online
Language: English
DBID source: FORM-1451807612, SCOPUS-84951744047
DOI: 10.1016/j.trc.2015.12.005
, Girault, Jan-Torben, Gayah, Vikash V., Guler, S. Ilgin, Menendez, Monica, 2016 >>
Author(s): Girault, Jan-Torben, Gayah, Vikash V., Guler, S. Ilgin, Menendez, Monica
Title: An exploratory analysis of signal coordination impacts on the Macroscopic Fundamental Diagram
Abstract: The Macroscopic Fundamental Diagram (MFD) of urban traffic is a recently developed tool to model and study large-scale urban traffic networks. The MFD of a network is significantly impacted by various properties of the network, including: signal green times, offsets, block lengths, travel speeds, and routing behaviors. However, the understanding of the impact of offsets (otherwise known as signal coordination) is limited to situations in which the network is linear. The impacts on two-dimensional networks are not well understood yet. To shed some light on this topic, this study examines the impacts of signal coordination on an idealized grid network using the AIMSUN micro-simulation software. Seven coordination strategies are considered, including: simultaneous, alternating, double alternating, one-dimensional green wave, two-dimensional green wave, MAXBAND, and random. In general, the impacts of coordination are highly sensitive to the cycle length of the network. The results also reveal that poor coordination can significantly decrease network capacity and free flow travel speed. However, good coordination offers little advantage over simultaneous offsets, even with directional demands traveling in the prioritized directions. The reason is that benefits provided to vehicles in the prioritized direction are offset by disadvantages to vehicles traveling in the non-prioritized directions. These results suggest that the insights from other idealized simulations with simultaneous offsets are generalizable to more realistic situations with better coordination strategies.2
Publication date / Date received: 2016-01-01
Event name: 95th Annual Meeting of the Transportation Research Board (TRB 2016)
Event date: 10-14 January 2016
Place: Washington D.C., USA
Language: English
DBID source: FORM-1454099537
, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): Guler, S. Ilgin, Menendez, Monica
Title: Pre-signals for bus priority: basic guidelines for implementation
Abstract: When compared to cars, public transportation (e.g., buses) can carry more people using less space. Hence, by increasing the share of people traveling by bus within an urban network, we can improve the efficiency of the urban transportation system, ultimately making it more sustainable. Unfortunately, buses operating mixed with cars can often get stuck in car congestion. One commonly used solution is to dedicate a lane for bus-use only. However, when bus flows are low, dedicated lanes running through intersections can reduce the discharge flows from these locations and lead to increased car delays, car queues, and all the negative externalities associated with congestion. This, in turn, can reduce the overall efficiency of the transportation network. Therefore, a solution is to discontinue the dedicated lane upstream of the main signal, removing bus priority at intersections. In this paper, we advocate the use of pre-signals upstream of signalized intersections to continue providing bus priority while minimizing the disruptions to car traffic. Pre-signals can allow buses to jump the car queues upstream of signalized intersections, while allowing cars to utilize the full capacity of the main signal when buses are not present. In this paper we provide practical guidelines on how to implement pre-signals at signalized intersections. Ideas on how to operate pre-signals are provided by using recent analytical and empirical findings from previous research on pre-signals. The reduction of system-wide (buses and cars) person hours of delay by using pre-signals, as compared to mixed-use lanes or dedicated bus lanes is also quantified. By doing so, the domains of application of pre-signals are also defined. This information can then be used to determine where and when pre-signals should be implemented in real urban networks and to quantify their benefits to the system.2
Published in: Public Transport
Volume: 7
Issue: 3
Pages: 339 - 354
ISSN: 1866-749X, 1613-7159
Publication date / Date received: 2015-12-01
Publication status: Dordrecht
Publication status: Published
Subjects: Pre-signals, Bus priority, Traffic flow, Signalized intersections
Language: English
Keyword: Pre-signals, Bus priority, Traffic flow, Signalized intersections
DBID source: FORM-1392995631, SCOPUS-84949219324
DOI: 10.1007/s12469-015-0104-9
, Yang, Kaidi, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): Yang, Kaidi, Guler, S. Ilgin, Menendez, Monica
Title: A transit signal priority algorithm under connected vehicle environment
Abstract: Transit signal priority is a cost-effective way to improve transit operations and reliability. Connected vehicles provide more precise and detailed information on vehicle movements, thus can be beneficial for transit signal priority. This paper proposes a transit signal priority algorithm using connected vehicle information. Simulation is conducted for different total flow, bus arrivals, bus occupancy and penetration rates. Results show that this algorithm successfully reduces the total passenger delay. It is also shown that this algorithm is not sensitive to the assumed occupancy, hence does not require accurate information on bus occupancy. Additionally, this algorithm significantly reduces the delay of buses with minimal increase to the delay of cars in the conflicting approach.2
Book title: 2015 IEEE 18th International Conference on Intelligent Transportation Systems (ITSC) : proceedings
Pages: 66 - 70
ISBN: 978-1-4673-6595-6
Publication date / Date received: 2015-01-01
Publication status: Piscataway, N.J
Publication status: Published
Event name: 18th IEEE International Conference on Intelligent Transportation Systems (ITSC 2015)
Event date: 15-18 September 2015
Place: Las Palmas de Gran Canaria, Spain
Language: English
DBID source: FORM-1446037784, SCOPUS-84950270968
DOI: 10.1109/ITSC.2015.19
, Yang, Kaidi, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): Yang, Kaidi, Guler, S. Ilgin, Menendez, Monica
Title: A signal control strategy using connected vehicles and loop detector information
Abstract: Connected vehicle technology can be beneficial for the operations of intersections. The informa- tion provided by cars equipped with this technology can be used to design a more efficient signal control strategy. This paper builds on a previous signal control algorithm (Guler et al., 2014) that used position information provided by connected vehicle technology. This paper considers both connected and traditional vehicles and integrates the connected vehicle algorithm with loop detector information to better accommodate low penetration rates.

Simulations are conducted for different total flows, demand ratios, penetration rates and locations of loop detectors. Results shows that the proposed algorithm outperforms an actuated signal strategy for most scenarios tested. For low demand scenarios, both average number of stops and average delay decrease as there are more connected vehicles. For high demands scenarios, this algorithm requires less than 50% penetration rates to outperform the actuated algorithm. If the loop detectors are installed a certain distance away from the intersection (30m), the algorithm outperforms the actuated algorithm for all demands, demand ratios and penetration rates.2
Publication date / Date received: 2015-01-01
Publication status: Ascona
Publication status: Published
Subjects: Connected vehicles, Traffic control, Intersections, Loop detector information
Event name: 15th Swiss Transport Research Conference, STRC 2015
Event date: April 15-17, 2015
Place: Ascona, Switzerland
Language: English
Keyword: Connected vehicles, Traffic control, Intersections, Loop detector information
DBID source: FORM-1432377936
, Stempfel, Julie, Guler, S. Ilgin, Menendez, Monica, Brucks, Wernher M., 2015 >>
Author(s): Stempfel, Julie, Guler, S. Ilgin, Menendez, Monica, Brucks, Wernher M.
Title: Effects of urban congestion on safety of networks
Abstract: The objective of this work is to understand if on urban roads, traffic safety can be linked to traffic congestion. To do so, crash data for the network of Zurich, Switzerland, is linked traffic data describing congestion from the same network. By aggregating the data, the crash risk in relation to traffic states is analyzed: (i) over the entire network for different times of day; and (ii) for individual links with different congestion levels. It is found that at the network level, the crash risk (number of crashes per car) is higher during times when the average network speed is lower (5-7 pm). Lower speeds are observed during this time period typically due to congestion. Hence, at the network level, there is evidence for congestion being an indicator of increased crash risk. During the same (congested) time period, it is also observed that crashes mostly happen on links with medium speeds, which could be due to higher speed variations within individual links during the congested time periods.2
Published in: Journal of Transportation Safety and Security
ISSN: 1943-9962, 1943-9970
Publication date / Date received: 2015-01-01
Publication status: Philadelphia, PA
Publication status: Accepted
Subjects: Safety, Urban Networks, Congestion
Language: English
Keyword: Safety, Urban Networks, Congestion
DBID source: FORM-1424109270
DOI: 10.1080/19439962.2015.1007193
Nebis system number: 006893087
, Menendez, Monica, Guler, S. Ilgin, Puffe, Enrico, 2015 >>
Author(s): Menendez, Monica, Guler, S. Ilgin, Puffe, Enrico
Title: Traffic flow at uncontrolled urban intersections with attention to different modes of traffic: Determination of representative standard values and interrelations
Abstract: Das in VSS-Norm SN 640 022 enthaltene Schätzverfahren zur Bemessung von Knoten ohne Lichtsignalanlagen berücksichtigt nur Konfliktsituationen zwischen Motorfahrzeugen. Da in diesem Verfahren die Einflüsse des öffentlichen Verkehrs sowie der Fussgänger und Velofahrer nicht berücksichtigt sind, kann diese Norm für städtische Verhältnisse nicht angewendet werden. Im Forschungsauftrag VSS 2008/301 wurde ein analytisches Verfahren entwickelt, welches die Berücksichtigung verschiedener Verkehrsarten an ungesteuerten Knoten ermöglicht. Die Methodik des neuen Schätzverfahrens basiert auf Sättigungswerten der vortrittsberechtigten und vortrittsbelasteten Motorfahrzeuge sowie auf den Zusammenhängen zwischen Sättigung und Verkehrsstärke an Konfliktpunkten. Diese wurden aufgrund von kurzzeitigen Zählungen in der Stadt Zürich geschätzt. Bei den in VSS 2008/301 angegebenen Sättigungswerten für öffentliche Verkehrsmittel, Fussgänger und Velofahrer handelt es sich um Erfahrungswerte. Diese Werte sind in der geplanten Untersuchung zu überprüfen. Zu diesem Zweck sind mittels empirischer Untersuchungen an Knoten mit Referenzcharakter die für schweizerische Verhältnisse repräsentativen Richtwerte zu ermitteln. Dabei sind Verhältnisse in verschieden grossen Städten zu berücksichtigen. Bei den Zusammenhängen zwischen Verkehrsstärke und Sättigung stehen die Wechselwirkungen im Vortrittsverhalten zwischen vortrittsberechtigten und vortrittsbelasteten Verkehrsteilnehmern am Konfliktpunkt im Vordergrund. Dazu sind entsprechende Schwellenwerte abzuleiten. Die Richtwerte der maximalen Sättigung vortrittsberechtigter und vortrittsbelasteter Fussgänger, Velofahrer, Trams und Busse können zudem aufgrund der Ergebnisse in den laufenden Forschungsarbeiten VSS 2007/306 und VSS 2007/305 verifiziert werden. Aufgrund der neuen Erkenntnisse ist ein Normentwurf zu erarbeiten. The estimation method contained in VSS standard SN 640 022 to the assessment of uncontrolled intersections takes into account only conflict situations between motor vehicles. Since in this method the influences of the public transport as well as the pedestrians and bicycles are not considered, this standard cannot be used for urban conditions. An analytical method which considers the different traffic types at uncontrolled intersections was developed in the research project VSS 2008/301. The methodology of the new estimation method is based on saturation values of the motor vehicles with the right of way and those that have to give way as well as on the coherences between saturation and traffic volume at conflict areas. These were valued due to short-time measurements in the city of Zurich. The saturation values regarding to the public transport, pedestrians and bicycles are based on experience. These values have to be checked in the planned research project. Therefore the reference values have to be determined by empirical studies at intersections with reference character for Swiss conditions. Conditions in towns of different size have to be taken into account. At the coherences between traffic volume and saturation the interactions between vehicles with the right of way and those that have to give way at conflict area are in the foreground. To this corresponding threshold values have to be derived. The reference values of the maximum saturation for pedestrians, bicycles, tramways and busses with the right of way and those that have to give way moreover can be verified due to the results of the ongoing research projects VSS 2007/306 and VSS 2007/305. Due to the new knowledge a new standard concept has to be worked out.2
Published in: Technical report VSS
Volume: 2011/308
Publication date / Date received: 2015-01-01
Publication status: Published
Language: English
DBID source: FORM-1454149808
, Menendez, Monica, Guler, S. Ilgin, Puffe, Enrico, 2015 >>
Author(s): Menendez, Monica, Guler, S. Ilgin, Puffe, Enrico
Title: Traffic flow at uncontrolled urban intersections with attention to different modes of traffic: Determination of representative standard values and interrelations
Abstract: Das in VSS-Norm SN 640 022 enthaltene Schätzverfahren zur Bemessung von Knoten ohne Lichtsignalanlagen berücksichtigt nur Konfliktsituationen zwischen Motorfahrzeugen. Da in diesem Verfahren die Einflüsse des öffentlichen Verkehrs sowie der Fussgänger und Velofahrer nicht berücksichtigt sind, kann diese Norm für städtische Verhältnisse nicht angewendet werden. Im Forschungsauftrag VSS 2008/301 wurde ein analytisches Verfahren entwickelt, welches die Berücksichtigung verschiedener Verkehrsarten an ungesteuerten Knoten ermöglicht. Die Methodik des neuen Schätzverfahrens basiert auf Sättigungswerten der vortrittsberechtigten und vortrittsbelasteten Motorfahrzeuge sowie auf den Zusammenhängen zwischen Sättigung und Verkehrsstärke an Konfliktpunkten. Diese wurden aufgrund von kurzzeitigen Zählungen in der Stadt Zürich geschätzt. Bei den in VSS 2008/301 angegebenen Sättigungswerten für öffentliche Verkehrsmittel, Fussgänger und Velofahrer handelt es sich um Erfahrungswerte. Diese Werte sind in der geplanten Untersuchung zu überprüfen. Zu diesem Zweck sind mittels empirischer Untersuchungen an Knoten mit Referenzcharakter die für schweizerische Verhältnisse repräsentativen Richtwerte zu ermitteln. Dabei sind Verhältnisse in verschieden grossen Städten zu berücksichtigen. Bei den Zusammenhängen zwischen Verkehrsstärke und Sättigung stehen die Wechselwirkungen im Vortrittsverhalten zwischen vortrittsberechtigten und vortrittsbelasteten Verkehrsteilnehmern am Konfliktpunkt im Vordergrund. Dazu sind entsprechende Schwellenwerte abzuleiten. Die Richtwerte der maximalen Sättigung vortrittsberechtigter und vortrittsbelasteter Fussgänger, Velofahrer, Trams und Busse können zudem aufgrund der Ergebnisse in den laufenden Forschungsarbeiten VSS 2007/306 und VSS 2007/305 verifiziert werden. Aufgrund der neuen Erkenntnisse ist ein Normentwurf zu erarbeiten.

The estimation method contained in VSS standard SN 640 022 to the assessment of uncontrolled intersections takes into account only conflict situations between motor vehicles. Since in this method the influences of the public transport as well as the pedestrians and bicycles are not considered, this standard cannot be used for urban conditions. An analytical method which considers the different traffic types at uncontrolled intersections was developed in the research project VSS 2008/301. The methodology of the new estimation method is based on saturation values of the motor vehicles with the right of way and those that have to give way as well as on the coherences between saturation and traffic volume at conflict areas. These were valued due to short-time measurements in the city of Zurich. The saturation values regarding to the public transport, pedestrians and bicycles are based on experience. These values have to be checked in the planned research project. Therefore the reference values have to be determined by empirical studies at intersections with reference character for Swiss conditions. Conditions in towns of different size have to be taken into account. At the coherences between traffic volume and saturation the interactions between vehicles with the right of way and those that have to give way at conflict area are in the foreground. To this corresponding threshold values have to be derived. The reference values of the maximum saturation for pedestrians, bicycles, tramways and busses with the right of way and those that have to give way moreover can be verified due to the results of the ongoing research projects VSS 2007/306 and VSS 2007/305. Due to the new knowledge a new standard concept has to be worked out.2
Published in: Technical report VSS
Volume: 2011/308
Publication date / Date received: 2015-01-01
Publication status: Zürich
Publication status: Published
Subjects: Ungesteuerte Knoten innerorts, Verkehrsablauf, Verkehrsqualität,, Leistungsfähigkeit, Sättigung, Uncontrolled urban intersections, Traffic flow, Level of service, Capacity, Saturation
Language: English
Keyword: Ungesteuerte Knoten innerorts, Verkehrsablauf, Verkehrsqualität,, Leistungsfähigkeit, Sättigung, Uncontrolled urban intersections, Traffic flow, Level of service, Capacity, Saturation
DBID source: FORM-1422627442, FORM-1454149808
, He, Haitao, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): He, Haitao, Guler, S. Ilgin, Menendez, Monica
Title: Providing Bus Priority Using Adaptive Pre-signals
Abstract: Bus priority is important in cities to encourage people to use public transport. However, providing a dedicated bus lane is not always feasible. It might not be the most efficient solution either, especially if bottlenecks such as traffic signals exist. This paper examines an alternative strategy to use an additional signal upstream of the main signal (a pre-signal) to provide bus priority at signalized intersections. Its primary purpose is to allow buses to jump the car queues before the intersection while cars can still use all the lanes at the main signal to fully utilize the capacity of the intersection. This paper formulates an online control algorithm to operate an intersection with such pre-signal infrastructure. The control algorithm is developed by determining the best operating strategy for the intersection at each demand level using a micro-simulation model in VISSIM. In a simulation case study, it is observed that compared to using a dedicated bus lane, the congestion upstream of the intersection during peak hours mitigated. Meanwhile, compared to using mixed-use lanes, the average person delay during the off-peak hours is lower and bus priority is provided. Therefore, it is concluded that implementing a pre-signal with the proposed online control algorithm provides a good balance between providing bus priority and sustaining car throughput.2
Book title: TRB 94th Annual Meeting Compendium of Papers
Volume: 15-2793
Publication date / Date received: 2015-01-01
Publication status: Published
Event name: 94th Annual Meeting of the Transportation Research Board (TRB 2015)
Event date: January 11-15, 2015
Place: Washington, DC, USA
Language: English
DBID source: FORM-1423770359
, He, Haitao, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): He, Haitao, Guler, S. Ilgin, Menendez, Monica
Title: Providing Bus Priority Using Adaptive Pre-signals
Abstract: How to dynamically implement different levels of bus priority at intersections while minimizing the negative effects on general traffic using: a dedicated bus lane, a pre-signal, or mixed lanes.2
Pages: 15-2793
Publication date / Date received: 2015-01-01
Publication status: Published
Event name: 94th Annual Meeting of the Transportation Research Board (TRB2015)
Event date: January 11-15, 2015
Place: Washington, DC, USA
Language: English
DBID source: FORM-1423071721
, Guler, S. Ilgin, Gayah, Vikash V., Menendez, Monica, 2015 >>
Author(s): Guler, S. Ilgin, Gayah, Vikash V., Menendez, Monica
Title: Providing Bus Priority at Signalized Intersections with Single-lane Approaches
Abstract: Signalized intersections often represent a major source of bus delays. One typical strategy to mitigate this problem is to dedicate an existing car lane for bus-use only to minimize the interactions between cars and buses. However, this is physically impossible at approaches where only a single travel lane is available for each direction. To this end, this research explores a novel method to provide priority to buses at signalized intersections with single-lane approaches through the use of additional signals in a way that (nearly) eliminates bus delays while minimizing the negative impacts imparted to cars. Using these signals, the bus can jump a portion of the car queue using the travel lane in the opposite direction. This paper theoretically quantifies the delay savings buses can achieve, and the negative impacts imparted onto cars when this pre-signal strategy is applied. The negative impacts are measured as the additional car delays experienced when the intersection signal is under-saturated, and the reduction in car-discharge capacity when the intersection signal is over-saturated. In the under- saturated case, the results show that moderate average bus delay savings (~5-7 seconds per vehicle) are achieved if the pre-signal is always in operation; and these results decrease the total system-wide delay (measured in person-hours) only if bus occupancies are very high. However, if the pre-signal operation is targeted to only provide priority to the buses that would benefit the most, significant bus delay savings can be achieved (delay benefits to buses which receive priority are about doubled) while also reducing the system-wide delay, even if the ratio of bus to car occupancy is relatively modest (greater than about 20). In the over-saturated case, bus delay savings can be much more significant than under-saturated cases (greater than 30 seconds per bus), and this delay saving can increase further for longer block lengths (greater than 100 m). However, the capacity of the intersection decreases by up to 25% during each cycle in which a bus arrives to the intersection. Simulation tests confirmed that the general trends and magnitudes of bus delay savings and negative impacts to cars hold for more realistic behaviors. The overall benefits are slightly smaller in the simulations, but nevertheless the strategy seems promising as a bus priority strategy at intersections with single-lane approaches in the field.2
Published in: Transportation Research Procedia
Volume: 9
Issue: 2015
Pages: 225 - 245
ISSN: 2352-1465
Publication date / Date received: 2015-01-01
Publication status: Amsterdam
Publication status: Published
Subjects: Bus priority, Pre-signal, Signalized intersection, Single-lane approaches
Language: English
Keyword: Bus priority, Pre-signal, Signalized intersection, Single-lane approaches
DBID source: FORM-1438773011
DOI: 10.1016/j.trpro.2015.07.013
Nebis system number: 010514383
, Arnet, Kathrin, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): Arnet, Kathrin, Guler, S. Ilgin, Menendez, Monica
Title: Effects of Multimodal Operations on Urban Roadways
Abstract: Public transportation (e.g., buses) can provide more efficient urban transportation systems by carrying more people in the same space. A commonly used solution to prioritize this mode is to dedicate a lane for bus use only. However, the changes in system capacity are not clear for the use of a dedicated bus lane instead of completely mixed-use lanes. Even if the capacity of the dedicated bus lane were not fully used, this strategy could still increase car capacity in the remaining lanes in two ways: (a) buses traveling on a separate lane would eliminate conflicting bus maneuvers and (b) the reduced number of lanes available for cars could reduce the number of lane changes and could smooth traffic. This paper empirically analyzes differences in car capacity between (a) a mixed-use scenario without the influence of buses and a dedicated-lane scenario and (b) a mixed-use scenario with and without buses. Results show that with mixed-use lanes the car capacity per lane remains the same as compared with a dedicated-lane scenario. However, in mixed-use conditions, the presence of a bus in traffic flow can reduce capacity by 20%. Based on these findings, a simple analysis is carried out to compare passenger delay at urban signalized intersections with a mixed use versus dedicated bus lane. It is shown that passenger delay can be reduced with use of dedicated bus lanes if bus occupancies are relatively high or if car demand is low.2
Published in: Transportation research record : journal of the Transportation Research Board
Volume: 2533
Pages: 1 - 7
Publication date / Date received: 2015-01-01
Publication status: Published
Language: English
DBID source: FORM-1454148675
DOI: 10.3141/2533-01
, Arnet, Kathrin, Guler, S. Ilgin, Menendez, Monica, 2015 >>
Author(s): Arnet, Kathrin, Guler, S. Ilgin, Menendez, Monica
Title: Effects of Multimodal Operations on Urban Roadways
Abstract: Public transportation (e.g., buses) can provide more efficient urban transportation systems by carrying more people in the same space. A commonly used solution to prioritize this mode is to dedicate a lane for bus use only. However, the changes in system capacity are not clear for the use of a dedicated bus lane instead of completely mixed-use lanes. Even if the capacity of the dedicated bus lane were not fully used, this strategy could still increase car capacity in the remaining lanes in two ways: (a) buses traveling on a separate lane would eliminate conflicting bus maneuvers and (b) the reduced number of lanes available for cars could reduce the number of lane changes and could smooth traffic. This paper empirically analyzes differences in car capacity between (a) a mixed-use scenario without the influence of buses and a dedicated-lane scenario and (b) a mixed-use scenario with and without buses. Results show that with mixed-use lanes the car capacity per lane remains the same as compared with a dedicated-lane scenario. However, in mixed-use conditions, the presence of a bus in traffic flow can reduce capacity by 20%. Based on these findings, a simple analysis is carried out to compare passenger delay at urban signalized intersections with a mixed use versus dedicated bus lane. It is shown that passenger delay can be reduced with use of dedicated bus lanes if bus occupancies are relatively high or if car demand is low.2
Book title: TRB 94th Annual Meeting Compendium of Papers
Published in: Transportation research record : journal of the Transportation Research Board
Volume: 2533
Pages: 1 - 7
ISSN: 0361-1981, 2169-4052
Publication date / Date received: 2015-01-01
Publication status: Published
Event name: 94th Annual Meeting of the Transportation Research Board (TRB2015)
Event date: January 11-15, 2015
Place: Washington, DC, USA
Language: English
DBID source: FORM-1422898116, FORM-1454148675
DOI: 10.3141/2533-01
Nebis system number: 000024408
, Gayah, Vikash V., Dixit, Vinayak V., Guler, Ilgin S., 2014 >>
Author(s): Gayah, Vikash V., Dixit, Vinayak V., Guler, Ilgin S.
Title: Relationship between mean and day-to-day variation in travel time in urban Networks
Abstract: The day-to-day reliability of transportation facilities significantly affects travel behavior. To better understand how travelers use these facilities, it is critical to understand and characterize this reliability for different facilities. Early work in this area assumed that the variance of day-to-day travel times (a measure of the inverse of reliability) increases proportionally with the mean travel time; i.e., as the mean travel time increases, travel time reliability decreases. However, recent empirical data for a single bottleneck facility and a small urban network suggest a more complex relationship that exhibits hysteresis. When this phenomenon is present, the variance in travel time is larger as the mean travel time decreases (congestion recovery) than as the mean travel time increases (congestion onset). This paper presents an elegant theoretical model to describe the variance of travel times across many days in an urban network. This formulation shows that the hysteresis behavior observed in empirical floating car data on urban networks should not be unexpected, and that it is linked to the hysteresis loops that often exist in the Macroscopic Fundamental Diagram of urban traffic. To verify the validity of this formulation, data from a micro-simulation of the City of Orlando, Florida, are used to derive an observed relationship with which to compare to theory. The simulated data are shown to match the theoretical predictions very well, and confirm the existence of hysteresis in the relationship between the mean and variance of travel times that is suggested by theory. These results can be used as a first step to more accurately represent travel time reliability in future models of traveler decision-making.2
Published in: EURO Journal on Transportation and Logistics
Volume: 3
Issue: 3-4
Pages: 227 - 243
ISSN: 2192-4384, 2192-4376
Publication date / Date received: 2014-10-01
Publication status: Berlin ; Heidelberg
Publication status: Published
Subjects: Hysteresis, Travel time reliability, Macroscopic fundamental diagram, Urban traffic network dynamics
Language: English
Keyword: Hysteresis, Travel time reliability, Macroscopic fundamental diagram, Urban traffic network dynamics
DBID source: FORM-1378462122
DOI: 10.1007/s13676-013-0032-2
, Theodoridou, Sofia, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): Theodoridou, Sofia, Guler, S. Ilgin, Menendez, Monica
Title: An analytical approach for modelling tolled bus lanes
Abstract: High-occupancy vehicle (HOV) and bus lanes have been widely implemented in several countries as a measure to reduce highway congestion, or provide bus priority, in urban or suburban transportation networks. While general use lanes can be congested, if flows in bus or HOV lanes are low, these lanes can be severely underutilized. If ordinary vehicles, such as cars, are allowed in the bus lane at certain rates and in exchange of some toll, however, an optimized operation for all lanes could be achieved. Hence, the aim of this paper is to provide a generalized solution regarding the allowance rate of cars in the bus lane, as well as the toll rates that should be applied.2
Publication date / Date received: 2014-04-01
Publication status: Ascona
Publication status: Published
Subjects: Bus lanes, Traffic operations, Tolled lanes
Event name: 14th Swiss Transport Research Conference (STRC 2014)
Event date: May 14-16, 2014
Place: Monte Verità, Ascona, Switzerland
Language: English
Keyword: Bus lanes, Traffic operations, Tolled lanes
DBID source: FORM-1400083177
, Theodoridou, Sofia, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): Theodoridou, Sofia, Guler, S. Ilgin, Menendez, Monica
Title: An Analytical Approach for Modeling Tolled Bus Lanes
Abstract: 2
Publication date / Date received: 2014-01-01
Publication status: Unpublished
Event name: 11th International Congress on Advances in Civil Engineering (ACE 2014)
Event date: October 21-25, 2014
Place: Istanbul, Turkey
Language: English
DBID source: FORM-1420729416
, Stempfel, Julie, Guler, S. Ilgin, Menendez, Monica, Brucks, Wernher, 2014 >>
Author(s): Stempfel, Julie, Guler, S. Ilgin, Menendez, Monica, Brucks, Wernher
Title: Effects of traffic conditions on safety of urban networks
Publication date / Date received: 2014-01-01
Publication status: Published
Event name: 93rd Annual Meeting of the Transportation Research Board (TRB 2014)
Event date: January 12-16, 2014
Place: Washington, DC, USA
Language: English
DBID source: FORM-1393332738
, Menendez, Monica, Guler, S. Ilgin, 2014 >>
Author(s): Menendez, Monica, Guler, S. Ilgin
Title: Capacity of multi-modal non-signalized urban intersections
Abstract: 2
Publication date / Date received: 2014-01-01
Publication status: Unpublished
Event name: VSS quarterly meeting
Event date: February 2014
Place: Zürich, Switzerland
Language: English
DBID source: FORM-1422646369
, He, Haitao, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): He, Haitao, Guler, S. Ilgin, Menendez, Monica
Title: Effects of Pre-Signals at an Isolated Intersection: Simulation Results
Publication date / Date received: 2014-01-01
Publication status: Monte Veritá, Ascona, Switzerland
Publication status: Published
Event name: 14th Swiss Transport Research Conference (STRC 2014)
Event date: May 14-16, 2014
Place: Monte Verità, Ascona, Switzerland
Language: English
DBID source: FORM-1401942331
, He, Haitao, Guler, Ilgin S., Menendez, Monica, 2014 >>
Author(s): He, Haitao, Guler, Ilgin S., Menendez, Monica
Title: The effects of pre-signals at an isolated intersection: Simulation results
Abstract: A pre-signal is an additional signal upstream of the main signal which can be used to provide bus priority. Its primary purpose is to allow buses to jump the car queues at the intersection while cars can still use all lanes at the main signal to fully utilize the capacity of the intersection. In this way, bus delay at the intersection is reduced without causing extra stress to the overall traffic. The effects of the pre-signals at an isolated intersection was analytically studied by Guler and Menendez and compared to empirical measurement. However, on the arterial and network level, it is very difficult to study the effects analytically and from our best knowledge there does not exist real work examples. Therefore a simulation model is needed. The goal of this research is to validate the simulation approach by showing that on the isolated intersection level a VISSIM simulation model calibrated with the collected empirical data produces similar results. Therefore, it can be used to understand the mechanism behind the operation of pre-signals and can provide direct visual insights into its effects on traffic flow. With the developed micro-simulation, the effect of the red time duration at the presence of buses could be examined. Recommendation could then be given regarding how long this red signal should be when implementing pre-signals.2
Book title: Proceedings of the 14th Swiss Transport Research Conference (STRC 2014)
Publication date / Date received: 2014-01-01
Publication status: Ascona
Publication status: Published
Subjects: Pre-signals, Bus priority, Bus operation
Event name: 14th Swiss Transport Research Conference (STRC 2014)
Event date: May 14-16, 2014
Place: Ascona, Switzerland
Language: English
Keyword: Pre-signals, Bus priority, Bus operation
DBID source: FORM-1400079045
, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): Guler, S. Ilgin, Menendez, Monica
Title: Evaluation of pre-signals at oversaturated signalized intersections
Abstract: One of the major causes of bus delays in urban environments are signalized intersections. A commonly used solution to give priority to buses at signalized intersections is to dedicate a lane for bus-use only. This strategy allows the bus to skip the car queues and minimizes the bus delay experienced due to the signal. However, especially for low bus flows, it can also waste valuable green time at signals and impose additional car delays. Overall, even when bus passengers enjoy reduced travel times, the total person hours of delay in the system (i.e., buses and cars) can increase due to excessive delays experienced by car users, particularly when total vehicle demand exceeds the capacity of the signalized intersection. To avoid this, and in order to utilize the full capacity of the main signal while still providing bus priority, the use of a pre-signal (i.e., an additional signal upstream of the main signal) has been proposed. The goal of this research is to quantify the benefits of using pre-signals in terms of system-wide total person hours of delays specifically for over saturated intersections. Theoretical formulae are developed to quantify the effects of a pre-signal on traffic flow, and these formulae are empirically verified. Using the theoretical model, the total delay with a pre-signal strategy is compared to the total delay of implementing a dedicated bus lane, or having fully mixed lanes. Bounds on bus to car occupancy ratios for which pre-signals provide the lowest delay as compared to a dedicated lane or mixed lane strategy are quantified. The end results show that for over saturated intersections, pre-signals are always better for the system than dedicated bus lanes. Moreover, they can decrease the total person hours of delay as compared to mixed lanes for large car demands.2
Published in: Transportation research record
Volume: 4
Issue: 2418
ISSN: 0361-1981, 2169-4052
Publication date / Date received: 2014-01-01
Publication status: Washington, D.C.
Publication status: Accepted
Subjects: Umwelt, Verkehr, Geographie|Environment, Traffic, Geography
Language: English
DBID source: FORM-1392996175
Nebis system number: 000024408
, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): Guler, S. Ilgin, Menendez, Monica
Title: Evaluation of Presignals at Oversaturated Signalized Intersections
Abstract: One of the major causes of bus delays in urban environments is signalized intersections. A commonly used solution to give priority to buses at signalized intersections is to dedicate a lane for bus use only. This strategy allows the bus to skip the car queues and minimizes the bus delay experienced due to the signal. However, especially for low bus flows, it can also waste valuable green time at signals and impose additional car delays. Overall, even when bus passengers enjoy reduced travel times, the total person hours of delay in the system (i.e., buses and cars) can increase due to excessive delays experienced by car users, particularly when total vehicle demand exceeds the capacity of the signalized intersection. To avoid this, and in order to utilize the full capacity of the main signal while still providing bus priority, the use of a pre-signal (i.e., an additional signal upstream of the main signal) has been proposed. The goal of this research is to quantify the benefits of using pre-signals in terms of system-wide total person hours of delays specifically for over saturated intersections. The total delay with this strategy is compared to the total delay of implementing a dedicated bus lane, or having fully mixed lanes. Bounds on bus to car occupancy ratios for which pre-signals provide the lowest delay as compared to a dedicated lane or mixed lane strategy are quantified. The end results show that for over saturated intersections, pre-signals are always better for the system than dedicated bus lanes. Moreover, they can decrease the total person hours of delay as compared to mixed lanes for large car demands.
Publication date / Date received: 2014-01-01
Publication status: Published
Event name: 93rd Annual Meeting of the Transportation Research Board (TRB 2014)
Event date: January 12-16, 2014
Place: Washington, DC, USA
Language: English
DBID source: FORM-1393333047
, Guler, S. Ilgin, Menendez, Monica, 2014 >>
Author(s): Guler, S. Ilgin, Menendez, Monica
Title: Analytical formulation and empirical evaluation of pre-signals for bus priority
Abstract: One of the major causes of bus delays in urban environments are signalized intersections. A commonly used solution to give priority to buses at signalized intersections is to dedicate a lane for bus-use only. However this strategy can waste valuable green time at signals and impose additional delays to cars, especially when bus flows are low. Overall, the total person hours of delays in the system (i.e., buses and cars) can increase due to excessive delays experienced by car users. To this end, an additional signal upstream of the main signal, called a pre-signal, can be used to better utilize the capacity of the main signal while still providing bus priority to reduce the system-wide person hours of delays.
The aim of this research is to analytically quantify and empirically evaluate the delays encountered by cars and buses with the use of pre-signals. The ultimate goal is to provide domains of applications for the proposed strategy. The paper presents analytical formulations to compute bus and car delays using queuing theory. The analytical models show that for a wide range of cases pre-signals can minimize the system-wide person hours of delays, as compared to dedicating a lane for bus-use only or operating buses and cars completely mixed. The analytical model is validated with empirical data collected at an existing pre-signal, which shows that the delay predictions of the model closely follow reality.
Published in: Transportation research Part B, Methodological
Volume: 64
Pages: 41 - 53
ISSN: 0191-2615
Publication date / Date received: 2014-01-01
Publication status: Amsterdam
Publication status: Published
Subjects: Verkehr und Transport|Traffic and Transportation, Pre-signals, Bus lanes, Transit priority, Traffic flow
Language: English
Keyword: Pre-signals, Bus lanes, Transit priority, Traffic flow
DBID source: FORM-1383127608, SCOPUS-84898678990, WOS-000336877300003
DOI: 10.1016/j.trb.2014.03.004
Nebis system number: 000006554
, Guler, Ilgin S., Menendez, Monica, Meier, Linus, 2014 >>
Author(s): Guler, Ilgin S., Menendez, Monica, Meier, Linus
Title: Using connected vehicle technology to improve the efficiency of intersections
Abstract: Information from connected vehicles, such as the position and speed of individual vehicles, can be used to optimize traffic operations at an intersection. This paper proposes such an algorithm for two one-way-streets assuming that only a certain percentage of cars are equipped with this technology. The algorithm enumerates different sequences of cars discharging from the intersection to minimize the objective function. Benefits of platooning (multiple cars consecutively discharging from a queue) and signal flexibility (adaptability to demand) are also considered. The goal is to gain insights about the value (in terms of delay savings) of using connected vehicle technology for intersection control. Simulations are conducted for different total demand values and demand ratios to understand the effects of changing the minimum green time at the signal and the penetration rate of connected cars. Using autonomous vehicle control systems, the signal could rapidly change the direction of priority without relying on the reaction of drivers. However, without this technology a minimum green time is necessary. The results of the simulations show that a minimum green time increases the delay only for the low and balanced demand scenarios. Therefore, the value of using cars with autonomous vehicle control can only be seen at intersections with this kind of demand patterns, and could result in up to 7% decrease in delay. On the other hand, using information from connected vehicles to better adapt the traffic signal has proven to be indeed very valuable. Increases in the penetration rate from 0% up to 60% can significantly reduce the average delay (in low demand scenarios a decrease in delay of up to 60% can be observed). That being said, after a penetration rate of 60%, while the delays continue to decrease, the rate of reduction decreases and the marginal value of information from communication technologies diminishes. Overall, it is observed that connected vehicle technology could significantly improve the operation of traffic at signalized intersections, at least under the proposed algorithm.2
Published in: Transportation research. Part C, Emerging technologies
Volume: 46
Pages: 121 - 131
ISSN: 0968-090X
Publication date / Date received: 2014-01-01
Publication status: Oxford
Publication status: Published
Subjects: Verkehr und Transport|Traffic and Transportation, Connected vehicle, Traffic control, Intersections, Traffic flow
Language: English
Keyword: Connected vehicle, Traffic control, Intersections, Traffic flow
DBID source: FORM-1403175234, WOS-000343387300008
DOI: 10.1016/j.trc.2014.05.008
Nebis system number: 000889058
, Guler, Ilgin S., Menendez, Monica, 2013 >>
Author(s): Guler, Ilgin S., Menendez, Monica
Title: Empirical Evaluation of Bus and Car Delays at Pre-signals
Abstract: One of the major causes of bus delays in urban environments are signalized intersections. A commonly used solution to give priority to buses at signalized intersections is to dedicate a lane for bus use only. This strategy allows the bus to skip the car queues and minimizes the delay experienced due to the signal. However, especially when bus flows are low, this strategy can waste valuable green time at signals and impose additional delays to cars. Overall, the total person hours of delay in the system (i.e., buses and cars) can increase due to excessive delays experienced by car users even when bus passengers enjoy reduced travel times. To this end, the use of pre-signals, which is an additional signal upstream of the main signal, has been proposed to utilize the full capacity of the main signal while still providing bus priority. When there are multiple lanes (2 or more) approaching the intersection, and one is dedicated for bus-use only, the idea is to discontinue this bus lane some distance upstream of the intersection. A pre-signal is used to stop cars at this location to provide bus priority. The pre-signal allows cars to use all lanes to discharge from the main signal, except when a bus arrives to this location. At that time, the pre-signal turns red for cars. This allows for buses to maneuver into the intersection without encountering conflicts from cars, and provides bus priority by moving them to the front of the intersection. While pre-signals have been proposed, to the authors' knowledge the realized benefits to buses, and dis-benefits to cars that arise from this strategy have not been quantified. Therefore, the goal of this research is to collect data to empirically quantify the delays encountered by cars and buses with the use of pre-signals. By doing so, a better understanding of the changes in car and bus operations due to interactions between these modes, and the effects of strategies to mitigate these effects can be obtained.
Publication date / Date received: 2013-01-01
Publication status: Published
Event name: 13th Swiss Transport Research Conference (STRC 2013)
Event date: April 24-26, 2013
Place: Ascona, Switzerland
Language: English
DBID source: FORM-1367320433
, Guler, Ilgin S., Menendez, Monica, 2013 >>
Author(s): Guler, Ilgin S., Menendez, Monica
Title: Empirical Evaluation of Bus and Car Delays at Pre-signals
Publication date / Date received: 2013-01-01
Publication status: Published
Event name: 13th Swiss Transport Research Conference (STRC 2013)
Event date: April 24-26, 2013
Place: Ascona, Switzerland
Language: English
DBID source: FORM-1369132184
, Guler, Ilgin S., Grembek, Offer, Ragland, David R., 2013 >>
Author(s): Guler, Ilgin S., Grembek, Offer, Ragland, David R.
Title: Using Time-Based Metrics to Compare Crash Risk Across Modes and Locations
Publication date / Date received: 2013-01-01
Publication status: Published
Event name: 92nd Annual Meeting of the Transportation Research Board
Event date: January 13-17, 2013
Place: Washington, DC, USA
Language: English
DBID source: FORM-1369308437
, Dixit, Vinayak, Gayah, Vikash, Guler, Ilgin S., 2012 >>
Author(s): Dixit, Vinayak, Gayah, Vikash, Guler, Ilgin S.
Title: Relationship between mean and variance of travel time in networks
Publication date / Date received: 2012-01-01
Publication status: Published
Event name: 1st European Symposium on Quantitative Methods in Transportation Systems (LATSIS 2012)
Event date: September 4-7, 2012
Place: Lausanne, Switzerland
Language: English
DBID source: FORM-1369308983

 

 

 

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