14.2.4 Transit

Transit can be analyzed using TDM outputs. Typical outputs for transit using TDM include ridership by line or by company among other typical vehicular outputs. There are two types of TDM models that can be used to analyze transit:
  • The Statewide Area Model includes a procedure to automatically generate a transit route system based on a scenario network. The Statewide Area Model short-distance mode share model applies different mode splitting factors to TAZs with different transit accessibility. The Statewide Area Model transit assignment procedure produces standard TransCAD outputs to help review transit ridership.
  • MPOs may have TDMs, whose outputs can also be used to analyze transit.
Transit can also be analyzed using microsimulation. Microsimulation excels at measuring transit’s impacts on other modes of transportation (and vice versa) and gives the flexibility to analyze various transit scenarios (e.g., transit stops in mixed traffic versus transit stops in an exclusive lane; transit stops downstream of intersection versus transit stops upstream of intersection; impacts of queue jumper or transit signal priority; complex transit facilities; etc.).
While a TDM or microsimulation can be used for analysis of most transit projects, the HCM 7th Edition has two chapters dedicated to transit analysis (see ). This methodology is limited to public transit vehicles, primarily buses and lightrail, operating in mixed or exclusive transit lanes that make stops along urban streets. The HCM method emphasizes LOS as a function of transit vehicle travel speed and transit riders’ perception.
The HCM methodology can be used if using microsimulation is not feasible due to resource constraints.
Table 14-35: Transit Analysis by Facility Type
Facility Type
HCM 7th Edition Chapter and Section Number
Urban street facilities
16.6
Urban street segments
18.6
The HCM transit analysis methodology for urban street segments has been integrated into HCS, which can be used to analyze transit if a microsimulation (microscopic) analysis is not feasible due to resource constraints. To conduct a transit analysis of urban street segments, the inputs shown below are collected and entered into the corresponding fields on the “Transit Mode - Streets” section of the Multimodal Input Data on HCS. Definitions of multimodal inputs are provided in the HCS User Guide. All other inputs (traffic, pedestrian, bicycle, etc.) for the intersection will impact LOS calculations for the analysis and are included. To view results, print the “segments report” found in the HCS.
  • Number of transit stops;
  • Dwell time, s;
  • Excess wait time, minutes;
  • Average passenger trip length, miles;
  • Transit frequency;
  • Passenger load factor;
  • Transit stops near side;
  • Transit top on-line;
  • Stops with shelters, proportion;
  • Stops with benches, proportion;
  • Re-entry delay, seconds; and
  • Base travel time rate, minutes/mile
There may be circumstances where microsimulation analysis is not feasible and the HCM methodology is not applicable. In such cases, the following methodologies can be used to analyze transit:
  • The transit analysis methodology found in NCHRP 616
    “Multimodal Level of Service Analysis for Urban Streets”
     Chapter 6 is based on how accessibility, wait time, and travel time impact the probability of users riding transit. This type of analysis is done manually and guidance on conducting this analysis is provided in the NCHRP report.
  • The Transit Capacity and Quality of Service Manual (TCRP Report 165) provides in-depth guidance for the largest variety of transit scenarios. Using this methodology, users can analyze buses, demand responsive transit, vanpool, rail transit, and ferry transit. Furthermore, this methodology includes transit in mixed, semi-exclusive, or exclusive traffic as well as transit on grade-separated facilities.