Flashing beacons (commonly called flashers or flashing lights) are frequently requested by communities in the belief that they will reduce vehicle speeds. Unfortunately, this is not necessarily the case. The following discussion of flashing beacons is offered in the interest of broader public understanding of what flashers can do and what factors must be considered before they should be installed.
EFFECTIVE USAGES OF FLASHERS
A flasher is generally installed at an intersection or in conjunction with a warning sign in advance of an area requiring greater than normal care by the average driver. Flashing beacons serve a useful purpose where the flashing yellow is used to alert drivers to unusual conditions that are not readily apparent, such as: obstructions in the roadway, uncommon roadway conditions, narrow bridges, or unusual conditions hidden from the motorists' view. One of the more common locations where a flasher can be used effectively is at a signalized intersection located just beyond a vertical or a horizontal curve, when the intersection is hidden from the view of approaching travelers. For any flasher to be effective, it must command the respect of the traveling public. In other words, immediately after seeing a flasher, the driver must consistently see an unusual condition which is being singled out for attention. Furthermore, the condition that the driver sees must be viewed as serious enough to justify his having been alerted.
When flashers are used improperly and installed at locations where they are not warranted, they soon lose much of their effectiveness. They simply cease to command the respect of the drivers. What happens is that after continually being alerted to a condition which seldom, if ever, appears to be truly unusual, drivers actually stop "seeing" the flasher. When this happens, flashers which are truly needed may well be disregarded by drivers who have become conditioned to believe that flashers are just "window dressing." Because of this normal human reaction, even one improper usage greatly reduces the effectiveness of essential flashers.
SYMPTOM vs. PROBLEM
Quite often, community requests for flashers are emotional responses to symptoms, rather than attempts to solve underlying problems. To put this into perspective, let's use an appropriate analogy: the case of measles. Obviously, to cure a patient who has measles, the disease itself (measles) must be treated - not the symptom (rash). In traffic control, it is not uncommon for public responses to be directed at treating symptoms. For example, in cases where concerned parents are requesting flashers on pedestrian warning signs, a traffic investigation all too frequently reveals that:
There is no "safe route to school" plan in the community.
There is no pedestrian safety program in the schools.
Very young children are allowed to travel to school by whatever route they prefer.
Parents are willing to abdicate their responsibilities by placing the entire burden for pedestrian safety on a traffic control device.
Local law enforcement officials turn a blind eye to pedestrian traffic violations.
Where traffic laws are enforced by conscientious law enforcement officials, parents claim that the fault lies in inadequate traffic control devices, not in their children's actions.
Flashers that are installed when these conditions exist result in the following:
The flasher soon becomes part of the normal driving environment and is ignored.
The community continues to avoid treating the real problem.
Other flashers, which are justified, are frequently disregarded by drivers conditioned to believe that flashers can be safely disregarded.
In summary, when flashers are properly located, they serve a useful function. When they are used improperly and installed in locations where they are not warranted, they soon lose much, if not all, of their effectiveness. More seriously, improper usage greatly reduces the effectiveness of other flashers installed in areas where there is a real need. Above all, it is essential to prove that there is a problem which can be solved through the installation of a flasher before actually employing one. Too often, flashers are installed when someone assumes there is, or is going to be, a problem. It is of the utmost importance that flasher installation be held to a minimum in order to maintain a high degree of respect for the flasher installations that are truly needed.
This document is based on a booklet called "Flashing Lights - Do they Really Slow Traffic?", published by the Arizona Department of Transportation.