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Why doesn't our city install more flashers to slow down traffic at pedestrian crossings?

Flashing yellow warning beacons, commonly called flashers, are frequently requested in the belief that they will reduce vehicle speeds and improve safety. Flashing beacons are generally helpful when used to alert drivers of an unexpected condition that is not readily apparent. These conditions can include obstructions in the roadway, narrow bridges or other unusual conditions hidden from the motorists' view. However, flashers must command respect of the drivers to be effective.

Warning flashers can be mounted over the road or along the side of the road, and accompanied by advance warning signs. A relatively new in-pavement flasher for crosswalks (sometimes called 'flashing crosswalks') is also available for use. Flashing crosswalks are approved in the MUTCD for marked crosswalks that are not controlled by traffic signals, STOP signs or YIELD signs. If used, in-roadway warning lights shall be installed along both sides of the crosswalk and span the entire length of the crossing.

While less expensive than traffic signals, flashers can be very costly ($30,000 to $50,000 to install plus ongoing operation and maintenance costs). Studies in urban areas show that flashers typically result in little if any reduction in driver speeds. Even studies of flashers as speed limit sign beacons (used to alert drivers of a lower speed limit when the flashing beacon is in operation) has only resulted in about a three mph speed reduction. This is despite a regulatory speed limit sign requiring a 15-mph to 20-mph reduction when flashing at school zone locations.

When flashers are used improperly or are overused, they soon loose much of their effectiveness. They cease to command the respect of the drivers if the driver does not consistently see the need for their use. If flashers are used, they should only flash during the times when crossings occur (e.g., such as during school crossing periods). This can be done with a time clock, pedestrian push button to activate the flasher, or through automatic pedestrian detection devices. If used at many locations in a community, the effectiveness of each flasher may be diminished as it becomes part of the normal driving environment and is ignored by drivers. The request for a flasher is often a symptom of the need for traffic safety education, training, or police enforcement in the community. Other types of traffic improvements, such as a 'Safe Route to School' plan, raised medians, advance warning signs or pavement markings, or parking removal should also be explored before installing a flashing warning beacon or 'flashing crosswalk'.

Learn about treatments to increase the safety of pedestrian crossings in our engineering section.