Buses may face challenging turning geometries when routed through small intersections, especially when transit service is operated in the curbside lane. Pulling the stop bar back from the intersection allows large transit vehicles to use two lanes around tight curb radii.
On-street parking and bikeways may provide space for a larger effective radius for transit vehicles to turn.
Where buses face challenging turning geometries in small intersections, especially when transit vehicles turn from curbside lane to curbside lane.
Allows buses to make wide turns in tighter intersections, and enables tighter intersection geometry to reduce the typical turning speed of general traffic.
Where the effective turning radius of the transit vehicle is greater than the radius provided for the transit vehicle to turn from one travel lane into one receiving lane, recessing the stop line allows the transit vehicle to briefly use the opposing lane to complete the turn.
Pedestrian safety and comfort is the most important turn radius consideration. Buses should only be used as a design vehicle for locations where buses turn frequently. If buses turn infrequently (such as during substitution, rerouting, or on low-frequency coverage routes), it is acceptable to allow buses to use the whole intersection for turns. On higher-frequency routes, use turn radii designed for buses, with other measures to reduce car turning speeds.
Recess the stop line on the receiving street to allow the turning bus to use the full width of the receiving street, accounting for the inner and rear swept paths of the bus.
For stop bars more than 20 feet from the intersection, install Stop Here on Red (MUTCD R10-6), and STOP pavement marking.
An advance stop bar can be applied with “STOP” stencil, as well as “Stop Here” sign (R1-5b).
“Chapter 3B.16 – Pavement and Curb Markings.” Manual on Uniform Traffic Control Devices, 2009 Edition. Federal Highway Administration, Washington, DC: 2009.
Plan transit routes to minimize difficult turns that might degrade the pedestrian environment and slow travel times (see Contraflow Transit Street).
Mountable curbs or “concrete pillows” may help to provide a smaller curb radius for slower target speeds, while allowing turns by large transit vehicles. Mountable curbs must be delineated with color or paving treatments that both prohibit cars from entering and alert pedestrians to look for buses.
Cement pillow, Portland (credit: Steven Vance)