A busway is a special roadway designed for the exclusive use of buses. A busway can be in its own right-of-way, or in a railway or highway right-of-way. Short stretches of streets designated for exclusive bus use are sometimes also called busways. A busway can also be built in an active rail corridor (example: Pittsburgh's East Busway). Busways usually have on-line stations, constructed so that there is room for overtaking stopping buses.
Busways provided fastest speeds if all intersections with roads are grade separated (overpass or underpass). At-grade intersections can be used (for example, the South Miami-Dade Busway), but care must be taken to avoid conflicts with cross traffic. If at-grade signalized intersections are used, traffic signal detectors can be installed to give buses a green signal when they arrive at the intersection. There is a danger that cross traffic will ignore traffic signals if they believe there is little traffic on the busway.
One advantage of busways is implementation flexibility: any portion of a busway can be put into service as soon as it is finished. Transit agencies can choose to start construction on the most favorable sections first, such as those that provide the most congestion relief or those that are easiest to build in terms of ownership and permitting. A bus route can operate on a combination of one or more sections of busway, in mixed traffic on arterials or expressways, or on reserved bus or HOV lanes on arterials or expressways.
Another advantage of busways is operational flexibility: many different types of routes can operate on the busway. One can group these into three different types of service: dedicated, express, and local. The dedicated service generally makes all stops along the busway and provides frequent service over the entire service day. Express service picks up passengers in residential areas and then enters the busway at any convenient point, making few or no stops to the major destination (e.g. CBD). Express service may operate only in peak hours. Local service consists of any local route which uses the busway for a portion of its route. Any size public transit vehicle can use a busway, from van or minibus to articulated bus, depending on the demand for that type of service at that time of day.
There are two theories of busway operation: trunkline and feeder or through-routing. Separate trunkline and feeder service is the mode familiar from rail systems, where it is the only option. Feeder routes converge on major busway stations where passengers transfer to the trunkline busway route. If feeder buses are scheduled as timed transfers, wait time is minimized and the possibility of transferring from one feeder to another is increased. The advantages of this system are that service is easier for passengers to understand, since all vehicles on the busway serve the same route, and that the need to create opportunities for buses to pass each other is less crucial. The major disadvantage is that many trips require a transfer, which is considered by most customers to be burdensome. Through-routed systems often eliminate the need to transfer. The operating approach can be changed depending on experience. Further, the operating system could vary by time of day.
Busway stations can be designed to have berths for several vehicles to stop simultaneously. A high level of station amenities is generally provided. Stop locations for feeder buses (if any) should be designed to minimize walking distance and exposure to the elements. A barrier-free transfer (where the entire station is a paid zone, including feeder bus boarding area) reduces the difficulty associated with transferring and speeds boarding, since all fares are prepaid at turnstiles and therefore all doors can be used for boarding and there is no time lost to fare collection while boarding.
On-line stations can provide shelter from rain and sun (particularly important in Miami), telephones, and maps.
Busway station siting is important both to attract riders and to attract station-area development. Many corridors potentially available for busways run through industrial areas which neither generate not attract many trips. When determining which corridors should be developed into a busway, the potentially worse routing, compared to transit riders origins and destinations, should be weighed against the potential for faster operating speeds.
Although busways are generally designed to be used by public transit vehicles, it is possible to permit other authorized vehicles to use the facility, such as emergency vehicles, passenger vans, carpools, or others, provided that such vehicles do not interfere with the operation of transit vehicles. Although emergency vehicles are generally allowed on busways, privately operated carpools and vanpools are not usually permitted. Although these facilities might be designed for such shared use, there is a concern that non-professional drivers might exceed speed limits, especially in areas with on-line stations.
Under certain conditions, development can be attracted to station areas. If a station area already has development which attracts pedestrian traffic (and therefore bus riders), it may be more likely to attract more development. In an area of mostly abandoned buildings, warehouses, and vacant lots, it is difficult to attract any development. A strong regional economy is also a necessary ingredient. Even if there is much development activity, an area adjacent to a transit station could be completely bypassed if it is viewed as too dangerous or otherwise inappropriate for development. The construction of large park and ride lots, especially surface lots, can in themselves be a barrier to development, since land is not available for other uses, and the station area may not conducive to pedestrian activity. Station-area development can also consist of the reuse or more intensive use of existing structures, even if no new structures are built. The development of even small-scale commercial services serving transit riders (for example, day care, cleaning, coffee cart or snack shop) can make transit use more desirable. Even if developers wish to build commercial (or residential) uses in the station area, local land use controls (zoning and subdivision regulation) may not permit them to do so. Those living adjacent to station areas may fear the effects of increased auto traffic associated with commercial use, or may prefer not to have apartments constructed which might lead to an increase in local taxes or a decline in services.
Ottawa has had success with siting busway stations in pre-existing shopping malls. Over time, surface parking was converted to increased development, facilitated by the accessibility provided by the busway. Siting a station adjacent to existing development makes the station a destination even before new development arrives. Passengers waiting to transfer can also make use of their transfer time in adjacent shops.
Busways and busway stations can be designed so that they can be converted to light or heavy rail if ridership increases to the point where buses can no longer accommodate the demand. Ottawa's transitway was designed to enable rail conversion.