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Transit Priority Measures - the Bus Bulb


Transit Priority Measures - the Bus Bulb

One of the drawbacks of transit is that it can take twice as long to travel between two particular destinations via transit as it would via car. How can we make transit go faster? The slowness of transit is generally caused by three things: frequency of bus stops, amount of dwell time at each stop, and traffic. Reducing delays means reducing the number of bus stops, the amount of time the bus spends at each stop, and the amount of time the bus spends in traffic. While the first and the third items in the above list are discussed in my article about how to speed up local bus service , the middle one - reducing the amount of time the bus spends at each stop - has not been fully explored. In addition to preventing cash payment on board the bus , we can speed up local bus service by installing a transit priority measure called a bus bulb. Frequently, bus stops are located in what people in the transit community call "pull-outs", curb cuts where buses can pull out of the lane of traffic to pick up and let off customers. In a bus bulb, the reverse is the situation - the curb is extended into the street to allow for a bus to pick up and let off passengers in the lane of traffic. The bus bulb has become an increasingly popular way to increase the speed of local bus travel, and are found in North American cities like Portland (OR), San Francisco, and Vancouver. Bus bulbs can cost from $15,000 - 55,000 to create.

Advantages of the Bus Bulb

The main advantage of a bus bulb is that it eliminates the time it takes for the bus to leave a stop and pull back into traffic. In some cases the time needed to return to the traffic flow can be thirty seconds or more. By eliminating the delay caused by reentering into traffic, installing bus bulbs at only a handful of stops can make a significant difference in bus travel time and reliability. In one congested Seattle corridor bus bulbs increased the operating speed of transit from 4.5 to 5.7 mph. In addition, by creating more sidewalk space at the bus stop a bus bulb creates room for more robust transit infrastructure that could include nice bus shelters, real time bus information signs, and other things. This additional space also helps separate pedestrians waiting for the bus from pedestrians just walking down the street - reducing sidewalk congestion. Reducing sidewalk congestion can also speed bus travel by decreasing the amount of time it takes each person to board the bus. Bus bulbs also increase pedestrian safety by reducing the width of the street people need to cross. Finally, by eliminating the space required for the bus to enter the parking lane or pull-out to reach a stop a bus bulb can shorten the distance required for a bus stop , potentially increasing the supply of street parking.

Disadvantages of the Bus Bulb

The main disadvantage of the bus bulb for the unenlightened American who still believes that the automobile must always have priority over all other transportation modes. But even if we do not care (or even celebrate) the fact that a bus bulb will slow down automobile traffic, we still have to worry about a bus bulb increasing accidents. Actually, it is by no means certain that bus bulbs slow down vehicular traffic - experience in San Francisco showed that vehicular traffic speed actually increased after some bus pull-outs were replaced with bus bays because buses pulling back into traffic sometimes used both travel lanes to do so.

Where to Locate Bus Bulbs

Bus bulbs are generally installed in areas with high bus patronage and pedestrian activity. They are also installed in communities that would like some form of traffic calming. Bus bulbs should always be located on streets with twenty-four hour parking.

Where to Not Locate Bus Bulbs

Generally, bus bulbs are not installed on streets with a speed limit equal to or greater than 45 mph / 70 kph due to the increased danger of rear end collisions. Additionally, due to the possibility of cars being trapped in an intersection behind a stopped bus nearside placement of bus bulbs is preferred . Bus bulbs should also not be installed at a location where the bus is turning right immediately after the bulb, as the bulb may interfere with the turning radius of the bus. Most places only put bus bulbs on streets where there are two lanes in each direction to allow vehicles to pass stopped buses. Bus bulbs are also not suitable as layover locations, as the bus is blocking traffic when stopped. Bus bulbs are also not necessarily compatible with high number of bicycles, and in areas with poor drainage, as water may pool in the space where the bus bulb joins the sidewalk.


Overall, bus bulbs are an excellent tool for the transit planner to use in creating faster transit operating speeds. When used in conjunction with the other transit priority measures mentioned above, bus bulbs can help a city achieve a "transit-first" policy. Two interesting questions that have yet to be answered: how do "yield-to-transit" laws enacted in such places as Florida and Ontario affect the re-entry time of buses into traffic? Do jurisdictions that enact "yield-to-transit" laws have as much need for bus bulbs as jurisdictions that do not have such laws?

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