Pre-Signals Speed Up Buses on Narrow Streets

Faster buses attract more riders and add capacity by speeding up travel, but sometimes street geometry doesn't accommodate dedicated bus lanes. "The democratizing force is a dedicated lane, which can allow buses to carry upwards of four times as many travelers per hour than a general traffic lane," reports Laura Bliss in CityLab.

When a street cannot accommodate a dedicated bus lane, as when there is traffic in both directions, no parking, and the street needs to remain two-way, one option to speed up buses is pre-signals. These traffic signals, currently in use in the United Kingdom and Switzerland, are placed before intersections and can stop traffic in both directions to let buses pass. These signals stop the cars, then the bus pulls into the lane formerly used for oncoming traffic to pass, as pictured in this animation.

"According to the simulations that the authors ran, the time-savings appears to be significant. Pre-signals can save bus travelers 5 to 7 seconds of delay per intersection at uncongested intersections, and up to 30 seconds of delay at congested intersections," Bliss reports.