GIS for Transportation: Principles, Data and Applications

9.1 DRT Overview


Transit organizations typically offer two distinctly different types of service: Demand Responsive Transportation (DRT) and fixed route transportation. Fixed route transportation operates according to prescribed routes and schedules whereas DRT does not. In this lesson, we will look at DRT. Fixed route will be covered in Lesson 10.

DRT is generally designed to provide curb to curb or door to door service for individuals who have special transportation needs such as seniors and persons with disabilities. The availability of DRT services can vary significantly from state to state and even county to county based on funding availability. DRT differs from taxi service in two fundamental ways:

  1. To use DRT, a rider must make an advance reservation (generally, at least 24 hours in advance).
  2. DRT is a shared-ride type service where multiple riders can be serviced at the same time and a rider is generally not taken directly from their point of origin to their point of destination. Consequently, DRT trips can have substantially longer ride time than taxi trips.

DRT services are generally designed to serve rural areas where fixed route transit is not practical due to low ridership and also to complement fixed route services for those who live near a fixed route but are unable to use it due to physical or cognitive limitations.

ADA Complementary Paratransit

The Americans with Disabilities Act (ADA) of 1990 prohibits discrimination against persons with disabilities in a number of areas including public transportation. The FTA has defined a series of requirements public transit providers need to meet to comply with the ADA. These requirements are found in Title 49 Part 37 of the Code of Federal Regulations (CFR). In these regulations, the FTA requires fixed route providers to provide DRT service, comparable to the level of service provided to individuals who are able to utilize fixed route services, to persons with disabilities. DRT services designed to address the needs of persons with disabilities is known as paratransit service. Specifically, bus or rail fixed route providers are required to offer paratransit services to individuals who are unable to use the fixed route service due to physical and/or cognitive limitations, who live within ¾ of a mile of a fixed route and are traveling to a destination which is also within ¾ of a mile of a fixed route. This requirement is challenging and costly for transit providers to fulfill. It applies to all providers, and not just those who are receiving federal funding. It is also an unfunded mandate in that FTA does not provide grant monies to transit agencies to help offset the cost of compliance. You’ll complete an assignment next week to evaluate the eligibility of a series of trips for complementary paratransit service.

Technologies for DRT Services

Providing DRT services in a way which is both cost effective and customer friendly is a very challenging task. The number of riders requesting service can vary substantially from day to day as can the trip origins and destinations. Service requests are initiated by riders through a call to a Customer Service Representative (CSR). Reservations typically need to be made at least 24 hours before service. Generally, the day before services are delivered, schedulers need to determine how to accommodate all of the reservations for the day with a limited number of vehicles and drivers. Further, the schedulers need to ensure a wide variety of constraints are met including promised pickup time, required drop off times (e.g., for medical appointments) and total ride time. On the day of service, dispatchers work with the drivers to ensure all trips are successfully completed. Drivers follow a trip manifest which defines which stops they will visit and the order in which they will visit them. Drivers also need to track a variety of data elements at each stop including arrival and departure times, the passengers boarding and alighting at each stop, the vehicle odometer reading, and the amount of money collected from each passenger.

Steps to request DRT services: schedule ride at least one day in advance, dispatch paratransit vehicle, pick-up rider, and take rider to destination.
Figure 1 - DRT Process
Credit: US Government Accountability Office

For all but the smallest providers, it would be very difficult to manage DRT service without technology. The most important technology which providers use is DRT software. Most DRT software assists the providers with all of the key tasks associated with delivering and reporting on the service. Many systems incorporate Automatic Vehicle Location (AVL) technology, which allows the dispatcher to monitor the location of all of their vehicles. This can be extremely useful in terms of ensuring drivers stay on task and follow the manifest. Some of the more sophisticated packages can do automated scheduling. These systems determine the best vehicle for a given trip reservation. DRT scheduling is very complex owing to the large number of variables involved, many of which are related to human behavior, and as a result, even software that can do automated scheduling cannot produce good schedules without significant scheduler oversight.

Interactive Voice Response (IVR) technology is also playing an increasingly important role in DRT operations. Typically, systems which incorporate IVR will configure the system to automatically call riders the night before a scheduled trip to remind them of the trip and give them an opportunity to cancel the trip. Systems will also generally automatically call the riders when the vehicle is approaching their location. These calls, known as imminent arrival calls, are valuable for both the provider and riders. Providers benefit because the calls ensure riders will be ready, and riders benefit since the calls give them a clear idea of when to be ready and eliminate the need for them to wait outside for a prolonged period. IVR plays a significant role in reducing “No-Shows” where the driver gets to a location to pick up a rider and the rider is not there. No-shows add additional costs to a service which is already expensive to provide.

Many providers give their drivers Mobile Digital Computers (MDC) which serve a variety of functions. More and more DRT software vendors are shifting to tablet technology instead of using proprietary hardware. MDCs provide additional communications with dispatch via canned or ad hoc text messages. The MDCs also generally present the trip manifest information to the driver in an electronic form and tell the driver their next stop location, how well they are adhering to the schedule, how many passengers should be boarding and alighting at each stop, and how much money they should collect from each person. The driver also uses the MDC to capture the information they need to collect such as the stop arrival time, the passengers who boarded and who alighted the vehicle at the stop, how much they collected from each rider, and what time they departed from the stop. MDCs can also be configured to provide the driver with turn by turn directions and eliminate the need for a separate GPS device.

Fare Structures

Transit agencies use a number of different methodologies to establish a fare structure for their DRT services. The three most common are listed below:

Flat – In a flat fare structure, as the name implies, the cost of the trip is the same regardless of origin and destination, assuming both are within the agency’s service area.

Zone Based – In a zone based fare structure, the agency divides its service area into zones. The zones are generally comprised of a series of concentric circles or a rectangular grid which blankets the service area. Fares are then established for each origin and destination zone.

Mileage Based – In a mileage based fare structure, the agency develops a series of mileage based tiers and associates a fare with each. The mileage associated with each trip depends only on the origin and destination and not on other pickups or drop-offs the driver may have performed while the passenger is on the vehicle. Consider the following example:

Ellen makes a reservation to go to the senior center on Monday at 10 am. On Friday afternoon, the agency’s scheduler is working with their paratransit software to finalize the driver manifests (i.e., schedules) for Monday morning. This process involves determining the most efficient way to deliver the service while at the same time observing customer service policies such as ensuring all riders get to their appointments on time and do not exceed the maximum onboard time established by the agency. On Monday morning, the drivers depart the transit agency and begin to execute the manifests (i.e., schedules) that have been prepared for them. The driver assigned to pick up Ellen arrives at her house to pick her up at 8:45 am. The driver then drives to Allen’s house to pick him up and on to Sue’s house to pick her up. He then drives to the VA hospital to drop off Allen and to Walmart to drop off Sue. Finally, he drives to the senior center and drops Ellen off at 9:50 am.

The driver may have visited many stops while Ellen was on the vehicle, but the mileage used for fare determination is based only on the route from her origin to her destination. When an agency uses a mileage based fare structure, they can base the mileage on the fastest route from origin to destination or the shortest distance route from origin to destination.

Assignment 9-1 (20 points)

In this assignment, you will complete Exercise 8 of ESRI’s ArcGIS Network Analyst Tutorial and review the help topic on the “Vehicle Routing Problem Analysis.” The Vehicle Route Solver illustrates the algorithms DRT software employs to help providers schedule DRT trips. As you’re completing the exercise, address the following items and submit your responses in the form of an M.S. Word document to Assignment 9-1 in Canvas.

  1. Once the analysis is complete, include a separate screen shot of each route. (3 points)
  2. For each route, list the number of orders it serviced and the total time for the route. (2 points)
  3. For each route, list the maximum number of passengers who were onboard at the same time. (Hint: Patients can have other riders who accompany them.) (2 points)
  4. Describe the impact of increasing the capacities of the routes. (3 points)
  5. Describe the expected impact of increasing the “MaxTransitTime” parameter for each Ordered Pair. (3 points)
  6. In regards to setting up route zones, discuss the difference between the two possible settings for the “IsHardZone” parameter. (2 points)
  7. Describe the “Route Seed Points Class” and describe the difference between static and dynamic seed points. (2 points)
  8. Define the meaning of the “Route Class” property named “Fixed Cost” and describe the impact it has. (2 points)
  9. The Route Zones you set up prevented the vehicles from crossing the bay. What other Network Analyst approach(es) might you have used to accomplish the same thing? (1 point)

Assignment 9-2 (15 points)

In this assignment, you’ll use Network Analyst to examine the revenue impacts of changing the way a transit agency calculates fares for DRT service. Address the items below, and submit your responses in the form of an M.S. Word document to Assignment 9-2 in Canvas.

ABC Transit, a fictitious transit agency in San Francisco, has a mileage based fare structure which is based on the following 7 tiers:

Fare Structure
Trip Distance (miles) Fare
<1 $8
1-1.999 $10
2-2.999 $15
3-4.999 $20
5-9.999 $25
10-19.999 $35
>=20 $50

ABC Transit bases the trip distance on the fastest route between the origin and destination. However, some riders have measured the distance of their trips themselves and have complained that ABC Transit is not using the correct mileage. To avoid these types of rider complaints, ABC Transit is considering using the short route to determine trip distances for fare determination. However, before doing so, they want to determine what impact this change will have on their annual revenue. In this assignment, you will use a day’s worth of trip requests to estimate the impacts on annual revenue. In practice, you would use a much larger sample of historic data (perhaps 3 months).

For this assignment you should complete the following steps:

  1. Create a new map document.
  2. Add the network dataset you created for San Francisco in Lesson 5.
  3. Download and unzip the TripODs shapefile which contains the origins and destinations for the trips ABC Transit delivered over the course of 1 day.
  4. Add the TripODs to the map document you created. Note that the TripODs feature class has attributes named “RouteID” and “Sequence.” “RouteID” is used to indicate which origins and destinations are paired together. “Sequence” is used to indicate their order. Features with a Sequence of 1 are origins and those with a Sequence of 2 are destinations.
  5. Use the Route Solver in Network Analyst to determine the trip distances based on shortest travel time:
    1. Create a new Route Solver analysis.
    2. Right click Stops in the Network Analysis window and select Load Locations.
    3. In the Load Locations dialog box make sure the TripODs feature class is specified in the “Load From” dropdown and that the RouteID field is mapped to the RouteName property in the “Location Analysis Properties” section of the dialog. Also select the Sequence field in the “Sort Field” dropdown. Click “Ok” to load the locations. After a short time, you should see that 734 stops were loaded.
    4. Open the Analysis Properties dialog (top right corner of the Network Analyst window) and set the Impedence to “Travel Time (minutes)” on the Analysis Settings tab. Also, check the Accumulation Attributes “TravelTime” and “Meters” on the Accumulation tab. Click “Ok” to close the window.
    5. Click the Solve icon on the NA toolbar to find the fastest route for each trip.
    6. Use the Copy Features tool to make a copy of the Routes feature class. Name the copy “FastestRoutes”.
    7. In the newly created FastestRoutes feature class, add two new fields. The first should be named “FastestDistance” (data type – double), and the second should be named “FastestFare” (data type – Short Integer).
    8. Use the field calculator to populate the newly created FastestDistance field with the trip distance in miles. (Hint: Use the Total Meters field and the conversion factor 1 mile=1609 meters.)
    9. Use the field calculator to populate the newly created Fastest Fare field. To do this select the Python parser, check the “Show Code Block” checkbox, and paste the following Python function into the “Pre-Logic Script Code” box:
      def Fare(TripDist):
        if TripDist < 1:
          return 8
        elif TripDist < 2:
          return 10
        elif TripDist < 3:
          return 15
        elif TripDist < 5:
          return 20
        elif TripDist < 10:
          return 25
        elif TripDist < 20:
          return 35
          return 50

      Then enter “Fare(!FastestDistance!)” in the lower box of the field calculator window. This will call the custom function you pasted in the “Pre-Logic Script Code” box. Click “Ok” to close the dialog and calculate the Fastest Fare.
    10. Examine the attribute table for the FastestRoutes feature class and enter the following data for Trips 113 and 139 into the Word document: Total_TravelTime, Total_Meters, FastestDistance, and FastestFare. (5 points)
  6. Rerun the analysis to find the shortest routes:
    1. Change the impedance to “Meters (Meters)” and click the Solve icon on the NA toolbar.
    2. Use the Copy Features tool to make a copy of the Routes feature class. Name the copy “ShortestRoutes”.
    3. In the newly created ShortestRoutes feature class add two new fields. Name the first field “ShortestDistance” (data type – double) and name the second “ShortestFare” (data type – Short Integer).
    4. Use the field calculator to populate the newly created ShortestDistance field with the trip distance in miles.
    5. Use the field calculator to populate the newly created ShortestFare field. To do this select the Python parser, check the “Show Code Block” checkbox and paste the following Python function into the “Pre-Logic Script Code” box:
      def Fare(TripDist):
        if TripDist < 1:
          return 8
        elif TripDist < 2:
          return 10
        elif TripDist < 3:
          return 15
        elif TripDist < 5:
          return 20
        elif TripDist < 10:
          return 25
        elif TripDist < 20:
          return 35
          return 50

      Then enter “Fare(!ShortestDistance!)” in the lower box and click Ok to close the dialog and calculate the Shortest Fare.
    6. Examine the attribute table for the ShortestRoutes feature class and enter the following data for Trips 113 and 139 into the Word document: Total_TravelTime, Total_Meters, ShortestDistance, and ShortestFare. (5 points)
  7. Use the Copy Features tool to make a copy of the FastestRoutes feature class. Name the copy “RouteCompare”.
  8. Add a new field to the RouteCompare feature class called “ChangeInRevenue”.
  9. Join the “ShortestRoute” feature class to the “RouteCompare” feature class.
  10. Use the field calculator to populate the ChangeInRevenue field with the difference between the ShortestFare and the FastestFare.
  11. Right click on the “ChangeInRevenue” field and select “Statistics”. How will the adjustment in fare determination methodology change the revenue collected for the day? (3 points)
  12. Assuming the day we analyzed is representative of their service throughout the year and assuming they operate 7 days a week, what is the expected annual impact of changing the fare determination method from fastest distance to shortest distance? (2 points)