A bus bulb, also called a bus boarder, bus border, bumpout, bus cape, or a kerb outstand is an arrangement by which a sidewalk or pavement is extended outwards for a bus stop; typically the bus bulb replaces roadway that would otherwise be part of a parking lane. With bus bulbs or boarders, a bus can stay in its traffic lane to discharge and pick up passengers, instead of having to pull over to the curb. The term bus bulb is prevalent in North American usage, whilst bus boarder or bus border is used elsewhere. A bus bulb or boarder can be considered as a specific form of curb extension, although that term is more normally used to describe a sidewalk extension for the purposes of traffic calming or other traffic management purposes.
Benefits
Benefits include preventing buses from being delayed by having to pull back into traffic, reducing risk of traffic collisions, reducing pedestrian exposure in crosswalks, reducing sidewalk congestion, providing space for bus patron amenities including bus shelters, and traffic calming. The protrusion also facilitates easier full length alignment of a bus entrance with a raised kerb stop, especially to allow level boarding in the case of low-floor buses. Bus bulbs also retain more parking when compared to a bus stop located in a parking lane, as a bus stop so located requires run-in and run-out tapers. Together these tapers may take up as much space as the actual stop, requiring parking to be prohibited over a longer length of road than with a bulb, where cars can park immediately on either side of the bus stop itself.
Drawbacks
The main drawback is for cyclists. The narrowing of the road can create danger for cyclists if the design does not take their needs into account. Where more than one lane exists in one direction, modelling has shown that there is no additional delay overall for following drivers, since the buses have shorter dwell times and since following vehicles may use the second lane for passing.
Prevent vehicles from parking in front of streetcar stops.
Increase standing room on the often restricted sidewalks at stop locations in some of the densest regions of the city.
Improve safety for passengers boarding and alighting at these stops; unmodified stops require passengers to step into traffic to board/alight. The safety concerns are mostly with regard to drivers who are inexperienced at driving among streetcars in mixed traffic.
Streetcar bulbs may also be beneficial at higher-capacity stops along other streetcar routes, and may be rolled out in conjunction with longer streetcars on the route.
