Around the world, cities are faced with the challenge of improving transit service in urban areas within the limited space available. Exclusive transitways for buses, minibuses, or light rail transit within existing street rights-of-way present a key approach to achieving that goal.
Those transit systems have the potential to greatly improve mobility in urban settings, however, there are usually significant planning and design challenges associated with making on-street priority transit facility projects come to fruition.
It is often the case that conceptual plans for on-street transit facilities are developed without a complete understanding of their physical requirements or the available design options. It is tempting to think that a street of fixed width can accommodate a transitway, stations, travel lanes, parking and landscaping without compromises. In reality, trade-offs must be made among these competing demands for street space.
Perhaps the greatest political challenge to implementing such facilities is the fact that a transitway introduced on an existing street will take space away from motorists. Existing travel lanes and on-street parking may need to be reduced and, in many cases, particularly outside of central cities, parallel streets are not available to provide an alternate route and absorb diverted traffic. The planning and design of on-street priority transit facilities must try to minimize these impacts as well as coordinate urban transportation, land use and urban design.
In an urban setting, on-street priority transit facilities can have different configurations, but they must have certain characteristics if they are to provide advantages over private cars or buses and streetcars operating in mixed traffic. Whether for bus, light rail, or jitney, on-street priority facilities must operate on the surface in an urban setting with crossing pedestrians and vehicular traffic, be primarily at-grade and provide a semi-exclusive right-of-way where transit vehicles operate free of competing parallel traffic.
The relationship between a transitway and surrounding land uses -- both transit-supportive land uses and those that conflict with a pedestrian-oriented environment -- is also critical to achieving the potential of priority transitways. Particular emphasis should be placed on areas immediately surrounding the stations, where access to land uses and pedestrian volumes are greatest. Reserving these areas for retail commercial uses, higher density employment and housing and entertainment will be mutually supportive of transit use.
At the same time, excluding automobile-oriented services and large parking lots from areas around the transitway will increase the pedestrian orientation of those areas best served by transit.
Urban design issues are also related to land use concerns, particularly as they affect the pedestrian-orientation of public spaces and the walking routes to and from the station. Located in the midst of the street setting, on-street transit facilities offer particular opportunities to coordinate the design of the facility and stations with their immediate context while encouraging development that contributes to the pedestrian character necessary for a transit system.
For example, monuments, special lighting, or distinctive design elements can create visual nodes that identify the location of transit stations. Impacts on retail activity must be considered also, particularly with relationship to parking, visibility and access. Fronting properties and buildings may require vehicular or pedestrian access from the road.
Such a requirement may place a constraint on transit engineering, but it can also create an opportunity for transit supportive land uses. To the extent that these frontages are automobile-oriented, with driveways and parking lots, or pedestrian oriented, with storefronts along the sidewalk, they can contribute to or detract from the transit environment.
If taking space away from motorists is the greatest political challenge to introducing a new transitway, the greatest design challenge is integrating the on-street transitway with surrounding vehicular traffic, including traffic crossing the transitway on cross streets and turning vehicles.
If a new transitway also reduces the number of available traffic lanes, it may result in secondary traffic impacts by diverting traffic to other parallel streets, which may then need to be modified to carry the additional traffic.
Numerous configurations for transitways within a street right-of-way are possible, including in the center of the roadway, on one side of it, or on both sides of the roadway.
The design of the transitway itself -- including striping, curbs, barriers, landscaping, distinctive paving, signage, lighting and catenary for light rail transit (LRT) or trolleybus -- affects the overall character of the corridor and may have either positive or negative impacts on its surroundings. For example, the placement of the transitway and its paving will affect the extent to which other vehicles intrude into the transitway and detract from transit operations.
The location and design of transitway stations also pose specific challenges in an on-street setting, particularly platforms, shelters, amenities and in-station fare control. On-street transit stops can be as simple as a small island or more elaborate.
Transit operations in an on-street transitway pose unique challenges as well. Operating speeds, signaling, traffic signal preemption, bus platooning, limited-stop service and passing of transit vehicles within the transitway can affect the quality of transit service, interact with surrounding traffic and pedestrians and impose specific design trade-offs due to space constraints.
Signage and signals for transit operators, motorists and pedestrians must be coordinated but distinct to facilitate safe operation. The key challenge is to provide signs and signals that are readily understandable to the public, including people who do not normally interact with such on-street transit facilities.
Parking, pedestrian circulation
On-street parking is invariably affected by the implementation of a transitway, with some or all of it being removed to provide much needed space. Where parking is retained, the available options and their impacts on transitway performance depend on the placement of the transitway within the street right-of-way. For example, curbside transit lanes essentially eliminate the possibility of parking, while transit in the median may allow parking either against the curb or next to the transitway.
Because travel by transit inherently involves a pedestrian component and a high-volume transitway concentrates pedestrian movement, the planning and design of on-street transit facilities must account for and facilitate pedestrian circulation and provide a pedestrian-friendly environment. Improved sidewalks, enhanced crosswalks, station platforms and bus loading areas can significantly affect pedestrian comfort and the public's experience with the transit service. Passenger queues also need to be accommodated to minimize conflicts with surrounding pedestrian circulation.
On-street transitways also impact utilities and emergency access. For instance, underground utilities may need to be relocated or alternate access may need to be provided. Catenary wires may need to be raised or relocated because they can affect overhead utilities or pose particular conflicts for firefighters, especially when adjacent multi-story buildings might require access by ladder trucks. Access for emergency vehicles must be provided for the benefit of both the transit facility and adjacent properties.
On-street priority transit facilities offer significant opportunities in cities that are looking for new approaches to improving mobility and the quality of life in a fiscally and physically constrained environment. In developing countries, on-street priority transit has special validity because population pressures are acute, ridership and dependence on public transit is substantial and funds for more capital-intensive responses are scarce.
In the U.S., where there is recognition that more cost-effective approaches to improved transit are needed, the Federal Transit Administration has encouraged more consideration of options like bus rapid transit, which often must be introduced into existing street corridors. It is attracting increased interest as a way to improve transit service without the costs associated with rail.
Proper planning for on-street transitways requires a holistic and multidisciplinary approach that combines consideration of transit facilities and service, vehicular traffic, pedestrian circulation, supportive land uses, station design, urban design, commercial and economic impacts, and impacts on the community and environment.
On-Street Priority Transit Facilities
Around the World
Priority transit facilities using primarily on-street exclusive transit lanes exist in
a number of countries around the world, including the following:
Brazil. Brazilian cities have led the world in developing on-street busways and have done the most experimentation with different configurations and operating schemes. Arguably, the city best known for its on-street priority transit system is Curitiba.
Curitiba's innovative on-street busway system enjoys a high degree of success because of coordination with overall roadway and land use planning. Each busway forms the spine of a "structural corridor" with parallel high capacity one-way arteries and adjacent high-density land uses.
Sao Paulo, which preceded Curitiba in busway development, now has four distinct on-street busway systems. Their different features and the various schemes tried over the years make Sao Paulo a veritable laboratory for the development of busways of different configurations and passenger and vehicle capacities.
Belo Horizonte and Porto Alegre also have developed urban busway corridors, including significant on-street segments.
Ecuador. Quito opened the first segment of its Sistema Integrado del Trole (Integrated Trolleybus System) in December 1995. The system, which uses articulated electric trolleybuses and high platform loading, has been extended to 13.9 miles. It carries 180,000 passengers each day.
A number of cities with transit systems that use mainly off-street alignments include shorter segments in exclusive on-street rights-of-way. These on-street segments are often in the downtown area to connect off-street LRT or busway alignments in outlying areas.
North American examples include LRT in Boston; Dallas; Denver; Los Angeles-Long Beach, Sacramento, San Diego, San Francisco and San Jose, California; Pittsburgh; Portland, Oregon; and Toronto, Calgary and Ottawa in Canada. Other cities with segments of on-street priority transit facilities mixed with off-street alignments include Istanbul, Turkey; Tunis, Tunisia; Cairo, Egypt; Manila, Philippines; Birmingham, Manchester and London, UK; and Cologne, Dresden, Hannover, Munich and Stuttgart, Germany.