Bus bulbs are sections of sidewalk that extend from the curb of a parking lane to the edge of the through lane. A major advantage of using bus bulbs is the creation of additional space at a bus stop for shelters, benches, and other bus patron improvements when the inclusion of these amenities would otherwise be limited without the additional space.

Several large cities on the West Coast have begun to explore bus bulbs as one of manhy strategies used in developing a transit preferential program. Researchers visited four transit agencies that use bus bulbs (San Francisco, Portland, Seattle, and Vancouver, British Columbia) to observe and document existing and planned bus bulbs. Before and after studies were conducted to determine if there was a change in pedestrian and traffic operations after the installation of bus bulbs. The bus bulb design was clearly an improvement in pedestrian space as compared to the bus bay design. The average amount of available spae for pedestrians and transit patrons alike improved from 19 to 44 square feet/pedestrian (1.8 to 4.1 sq m/ped) after the bulb was constructed. The replacement of a bus bay with a bus bulb improved cehicle and bus speeds on the block. The block with the farside stop saw a statistically significant increase in vehicle travel speed during both nonpeak (9.5 to 15.7 mph [15.3 to 25.3 km/h]) and peak (11.4 to 20.9 [18.4 to 33.6 km/h]) periods.