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Evolving Strategies for Demand Responsive Transit

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For people who are unable to drive or use conventional transit (e.g., fixed route buses and trains), getting around can be a real challenge. One group is receiving increasing attention in the transportation community: people with physical or mental disabilities that prevent them from being able to use existing buses and trains. The Americans with Disabilities Act of 1990 (ADA) requires transit agencies to operate curb-to-curb paratransit with ¾ mile of fixed route bus services for these. Although ADA paratransit constitutes only 1% of transit trips in U.S., the services make up 8% of the operating costs. Furthermore, demand for ADA paratransit increased by 41% from 2000 to 2010, and the trend of increasing demand and increasing cost is expected to continue as the American population gets older [1]. This presents a major challenge for transit agencies: equitable service must be provided for customers with disabilities, but increasing costs threaten the ability of agencies to continue providing adequate ADA paratransit along with conventional services. Recent and ongoing research at UMass Amherst addresses multiple strategies for managing ADA paratransit needs.

One way to approach the problem of mounting paratransit costs is to focus on optimizing the operations. Recent studies of ADA paratransit demand and operation patterns in New Jersey have shown that the total operating cost in a service region can be modeled based on the area of the region, the rate that trips are requested per time, and the allowable time window for an on-time pick-up [2].  There are ways to geographically align service regions to cover large areas in order to minimize the negative effects of making customers transfer.  It can be beneficial to break up large regions into zones such that one zone provides service within a dense urban core, and another zone provides service to more distributed areas [3].

Another approach to the problem is to manage demand by incentivizing users to travel at times of day when there is excess system capacity. The current ADA regulation requires agencies to schedule paratransit service within one hour of the customer’s requested pick-up time and to charge no more than 1.5 times the fare of conventional transit service. Peaks in demand at certain times of day leave agencies with no choice but to purchase more vehicles and hire more drivers, but these resources are costly when they go unused at other times of day. A time-varying fare, within the ADA constraints, could incentivize users with flexible schedules to travel at less costly times of the day to improve the system’s overall efficiency [4].

An emerging question is what role existing ADA paratransit should play in serving this population in the long term. We know that shared-ride services are most efficient in areas with dense demand.  In the suburban fringe, there are many trips that could be served more cost-effectively by taxis or on-demand mobility services (e.g., Uber, Lyft). In the Boston area, where the average cost of serving a one-way paratransit trip is $46.88, the MBTA is piloting a program to subsidize taxi trips for some users [5]. Despite concerns about vehicles being physically equipped and drivers having appropriate training to serve customers with disabilities, demand responsive services that allow vehicles to be shared by multiple user groups hold great promise for bringing down the cost of providing high-quality ADA paratransit service. Perhaps the changes that emerging technologies are bringing for mobility services will be a great equalizer that can afford the same transportation choices to people with disabilities as the rest of the general public. One thing is certain, the future users are going to require flexible and efficient transportation systems to meet their diverse needs.

By: Dr. Eric Gonzales

  1. American Public Transit Association (APTA) (2012). 2012 Public Transportation Factbook. Available online from: http://www.apta.com/resources/statistics/Documents/FactBook/
    APTA_2012_Fact%20Book.pdf
  2. Rahimi, M., Amirgholy, M., Gonzales, E.J. (2014). Continuum approximation modeling of ADA paratransit operations in New Jersey. Paper Number 14-4864. Transportation Research Board 93rd Annual Meeting, 12–16 January, Washington, D.C.
  3. Rahimi, M., Gonzales, E.J. (2015). Systematic evaluation of zoning strategies for demand responsive transit. Paper Number 15-4023. Transportation Research Board 94th Annual Meeting, 11–15 January, Washington, D.C.
  4. Amirgholy, M., Gonzales, E.J. (2015). Demand responsive transit systems with time dependent demand: User equilibrium, system optimum, and management strategy. Transportation Research Part B, doi:10.2016/j.trb.2015.11.006.
  5. Massachusetts Bay Transportation Authority (MBTA). Riding the T. Available online from: http://www.mbta.com/riding_the_t/accessible_services/?id=7108

Pre-signals for Transit Priority

Transit preferential treatments can reduce transit delay and therefore improve the efficiency and reliability of transit systems. Examples include dedicated bus lanes, queue jump lanes, and transit signal priority. However, these treatments are not always feasible due to lack of funding or space. In addition, they can often have detrimental impacts on other users of the system. Sustainability goals that are set by a lot of planning and transit agencies demand solutions that more efficiently utilize existing infrastructure and capacity while providing priority to transit vehicles.

Pre-signals allow for provision of priority to buses traveling on dedicated bus lanes by taking advantage of existing infrastructure and utilizing intersection capacity more efficiently. Pre-signals are additional signals placed upstream of signalized intersections to facilitate provision of some level of priority to buses, as well as other modes, by allowing them to bypass standing queues of cars. Typically, operating pre-signals require the existence of at least two lanes in the direction of travel.

However, recent work has suggested that pre-signals can aid in the temporary utilization of contra-flow lanes for transit priority provision for single lane approaches [1]. In particular, pre-signals are used upstream of the main intersection signals to allow the bus to jump the car queues and be at the front of the queue at the main signal. Pre-signals are used in combination with dedicated bus lanes when there is a need to end the bus lane in advance to allow cars to discharge from the intersection using all lanes. For example, as seen in Figure 1 the dedicated bus lane ends at some distance upstream of the intersection to allow cars to use all three lanes while discharging from the intersection.

Picture1

Figure 1. Pre-signal at a three-lane approach with a dedicated bus lane.

The pre-signal works as a regular signal and is coordinated with the main signal to utilize maximum capacity. While the main signal is red, cars receive a red light at the pre-signal and are queued upstream of it. This ensures that a bus arriving during the red period can move to the stop line at the main signal and discharge immediately when the main signal turns green. Cars receive a green pre-signal such that no gaps are created in the traffic stream, and no green time at the main signal is lost when buses are not present. Regardless of the main signal’s phase, a bus approaching the intersection will trigger the pre-signal to turn red for cars, allowing the bus to move to the main signal without encountering conflicting maneuvers from cars.

An example of real-world pre-signal operations can be seen in this video. The video presents the operation of a pre-signal along Langstrasse in Zurich, Switzerland. A dedicated bus lane and one lane for cars exist upstream of the intersection but merge into a single mixed-use lane just upstream of the signalized intersection. A pre-signal at the location of the merge provides priority to buses when approaching the main signal. The pre-signal turns red when the bus is detected approaching the intersection. As a result, the bus travelling on the bus lane can bypass the queue of cars and enter the mixed-use lane at the intersection before the cars arrive. As soon as the bus bypasses the standing queue of cars, the pre-signal turns green again so that cars can proceed through the intersection after the bus.

The concept of pre-signals was first introduced to address lost time due to acceleration and perception/reaction time at the onset of green at signalized intersections and the first pre-signals were installed in Dusseldorf, Germany in 1954 [2]. This first study found that if there are only cars in a traffic stream, the equivalent of approximately 4 seconds of additional green time can be gained at intersections with the use of this type of pre-signal. More recent work has explored the use of pre-signals to increase intersection capacity by resolving various types of vehicular conflicts (e.g., between left and through moving vehicles that are either conflicting or compete for green time at the main signal) that would otherwise occur at the signalized intersection downstream [3,4]. A theoretical analysis of pre-signals for transit priority was first presented by Wu and Hounsell [5]. However, their proposed implementation included a constant pre-signal operation regardless of the arrival of a bus. To the best of our knowledge, real-world implementations of pre-signals are limited. A few locations are known in London, operating in a fashion similar to the one described in [5] and one location has been noted in Zurich, Switzerland.

We are currently working on identifying domains of application for implementation of individual transit preferential treatments or combinations of those for a variety of operating conditions for traffic and transit. Click here for a relevant presentation. 

By: Eleni Christofa, Ph.D., Assistant Professor, UMass-Amherst and S. Ilgin Guler, Ph.D., Assistant Professor, The Pennsylvania State University 

[1] Guler, S.I., Gayah, V.V. and Menendez, M., 2016. Bus priority at signalized intersections with single-lane approaches: A novel pre-signal strategy. Transportation Research Part C: Emerging Technologies63, pp.51-70.

[2] Von Stein, W., 1961. Traffic flow with pre-signals and the signal funnel. Theory of Traffic Flow, Elsevier, Amsterdam.

[3] Xuan, Y., Gayah, V., Cassidy, M. and Daganzo, C., 2012. Presignal Used to Increase Bus-and Car-Carrying Capacity at Intersections: Theory and Experiment. Transportation Research Record: Journal of the Transportation Research Board, (2315), pp.191-196.

[4] Xuan, Y., Daganzo, C.F. and Cassidy, M.J., 2011. Increasing the capacity of signalized intersections with separate left turn phases. Transportation Research Part B: Methodological45(5), pp.769-781.

[5] Wu, J. and Hounsell, N., 1998. Bus priority using pre-signals. Transportation Research Part A: Policy and Practice32(8), pp.563-583.

 

T-Force Toolkit : Increasing Truck and Bus Traffic Enforcement

For a variety of reasons, routine traffic stops with large trucks and buses occur significantly less than traffic stops with passenger vehicles. Considering the detrimental effects of these crashes, it is critical that we incorporate truck/bus traffic enforcement into existing highway safety activities.

With this growing issue in mind, the University of Massachusetts Traffic Safety Research Program (UMassSafe) developed T-Force, Truck and Bus Traffic Enforcement Toolkit, providing a free one stop shopping tool for resources geared toward traffic patrol officers. T-Force is a three-part program with a goal of increasing the enforcement of moving violations such as speeding and lane violations. Different than programs aiming to inform specialized Motor Carrier Safety Assistance Program (MCSAP) officers, this information is intended for a wider audience, particularly officers conducting regular traffic enforcement.

The T-Force Toolkit is comprised of three main sections; including Fast Facts, Instructors Portal and Web Resources.

  • Fast Facts: This section of the Toolkit offers detailed information regarding the importance of traffic stops with trucks/buses, strategies for maintaining officer safety, how truck/bus traffic stops are different than those with passenger cars, the process of conducting an effective traffic stop and the details involved in CDL. Users can move quickly through this interactive tool, accessing only the information they need.
  • Instructors Portal: This section provides access to all of the materials needed to conduct the Safe and Effective Traffic Stops: Truck and Bus Traffic Enforcement training. This training, developed by UMassSafe, is currently being taught in several states across the country for local and state traffic patrol officers. Instructors can access all course materials on the website, including a guide for both instructors and participants as well as the PowerPoint presentation.
  • Web Resources: The web resources section provides access to an online library of videos, a discussion board to ask and answer questions, and links to other trainings and online resources.

For additional information  www.tforcetoolkit.com.

UMassSafe is a multidisciplinary traffic safety research group housed in the UMass Transportation Center at the University of Massachusetts. With the unique ability to examine highway safety from a variety of perspectives, UMassSafe provide tools and information in a format that is practical for a wide range of users from law enforcement personnel to statisticians at federal agencies. Working on issues related to commercial motor vehicle safety for over 15 years, UMassSafe has developed data query tools, crash corridor maps, and police training as well as conducted extensive crash data analysis and data quality improvement projects.

Written by Robin Riessman and Jennifer Gazzillo, UMassSafe