22.1 Overview

This chapter discusses the use of transit vehicles in the design of transportation corridors. The chapter includes the following sections and subsections:
22.1 Overview
  • 22.1.1 General Need;
  • 22.1.2 Types of Transit;
  • 22.1.3 Examples of Transit Agencies; and
  • 22.1.4 Transit Accommodation.
22.2 Right of Way Requirements
  • 22.2.1 Passenger Platforms;
  • 22.2.2 Intersections;
  • 22.2.3 Transit Centers; and
  • 22.2.4 Dedicated Transitways.
22.3 Roadway Design
22.3.1 Lane Widths;
22.3.2 Profiles;
22.3.3 Vertical Clearances;
22.3.4 Acceleration and Deceleration; and
22.3.5 Transit Stops.

22.1.1 General Need

Highways and streets must often accommodate transit vehicles as well as passenger cars and trucks. Owners of transportation corridors, such as the State of Texas, counties, and cities are responsible for managing, funding, and coordinating the design and construction of these facilities with transit agencies. TxDOT’s Public Transportation Division (PTN), as well as metropolitan transit authorities administer transit funds to ensure operation within the legal requirements in accordance with the Federal Transit Administration (FTA) regulations.
The incorporation of public transit vehicles and transit facilities requires that the roadway footprint include loading and unloading platforms, provisions for barrier-free access to and from these platforms, sufficient lighting and clear lines of sight to discourage crime. Sufficient space for additional facilities that support multi-model connections, such as shelters, ticket vending machines, shared micromobility docks, and passenger vehicle parking should also be included. These needs to accommodate public transit go beyond the basic connectivity and mobility considerations of traditional roadway design. The design of roadways that include dedicated transit corridors must be able to integrate not only the geometric needs of both existing and proposed transit vehicles, but also must include provisions in the footprint and typical section to accommodate the pedestrians, bicyclists, and micromobility users that will be travelling alongside the roadway to connect to the transit facilities. The design must encourage safety Table of Contents Instructions Reference Links Roadway Design Manual | 22-2 and healthy development for all transportation users, including vehicle free facilities in the public right-of-way such as multi-use pathways.
Chapter 3
discusses contextual impacts to be considered in design and implementation of transit facilities.

22.1.2 Types of Transit

The highest capacity types of transit include steel wheel on steel rail systems such as:
  • Commuter rail, usually running on shared freight lines and pulled by diesel locomotives;
  • Urban subway powered by third rail;
  • Urban and suburban light rail powered by overhead catenary; and
  • Suburban rail powered by on-board diesel engines.
These systems generally have high speed and high capacity which can require considerable capital investment. These systems usually occupy independent corridors, but sometimes may be designed in public roadway corridors.
At the other end of transit are traditional highcapacity buses and smaller passenger vans (also referred to as microtransit) that use public roadways and are mixed into the general-purpose traffic. These often run on local and rural roads. In general, bicycle, pedestrian, and micromobility devices fill the need for first mile/last mile connections completing a transit trip. Additionally, some buses can be configured for express between two points and travel freeways, toll roads, or managed lanes. These often require minimal capital investment other than the buses, bus maintenance facilities, and furniture for bus stops.
In-between rail and buses are new innovative transit approaches such as Bus Rapid Transit (BRT). This combines the low capital cost of existing roadway assets with the efficiency and capacity of dedicated transitways. This approach was pioneered in Curitaba, Brazil as early as 1974 and included dedicated roadway for the bus vehicles, level boarding with wide doors, pre-payment at loading platforms, and articulated buses. BRT quality is ranked by the Institute for Transportation & Development Policy (ITDP) and includes criteria for engineering, planning, operations, stations, communications, and access. Full BRT systems that essentially operate as traditional rail transit are given higher scores while “BRT-light” systems that only incorporate portions of the BRT concept are given lower scores.
As technology improves, newer types of public transit may emerge. Examples might be ondemand transit using autonomous vehicles, EV transit vehicles, point-to-point autonomous vehicles designed for one or two passengers, driverless smaller vehicles on dedicated transitways with more frequent service, etc.

22.1.3 Examples of Transit Agencies

Examples of major transit agencies around Texas include major public agencies such as Dallas Area Rapid Transit, Metro (Houston), CapMetro (Austin), VIA (San Antonio), Trinity Metro (Ft Worth), and SunMetro (El Paso) as well as rural transit agencies such as McKinney Avenue Transit Authority, Galveston Island Table of Contents Instructions Reference Links 22-3 | Roadway Design Manual| 2024 Transit, Brazos Transit District, etc. Intercity Bus private operators such as Greyhound, Megabus, and Vonlane are often used to connect major urban areas, Each agency has a different mix of transit modes including light rail, commuter rail, bus rapid transit, ondemand, microtransit, and traditional bus. These agencies may also have their own design manuals with criteria specific to transit design which should be considered alongside the TxDOT RDM. If the criteria conflict, it should be resolved prior to any significant design activity taking place.

22.1.4 Transit Mix

Design of roadways to accommodate transit vehicles can include traditional mixed traffic and curbside/shoulder bus stops, mixed traffic with protected areas for passenger loading/unloading, mixed traffic with priority to transit vehicles, dedicated at-grade guideways within the roadway section, and dedicated atgrade and elevated guideways using an independent corridor. A transit corridor may even contain a mix of these modes within the same corridor depending on the available ROW and cost/benefit analysis of the transit service.

22.1.5 Transit Accommodation

Design of the roadway section for transit vehicles includes areas beyond the pavement limits, such as adequate safety buffers between roadway and sidewalks, space for trees outside the clear zone behind curb to shade sidewalks, areas where bike sharing docks or microbility parking can be installed, space for shelter, information, and ticket vending, etc. It is important for roadway design engineers to coordinate with other urban design disciplines to avoid precluding current and future transit needs with incompatible geometry or roadway section. Transit design should also accommodate Vulnerable Road Users (VRUs).