Studies show that adjusting speeds by as little as 2 to 5 mph may save lives in pedestrian-related accidents. Photos: Information Display Co.
Scheduled to turn on automatically during school hours, a radar display takes the guesswork out of speed limits.

Other features — such as power source — also impact effectiveness. Figure out how and where the display will be used to decide between battery or solar power.

Battery-operated signs are one solution for locations where hard-wired power sources aren't readily available. For instance, if you plan to mount the display temporarily on the trunk of a patrol car or other vehicle, you may want a display that can be powered directly from that vehicle's battery.

However, batteries require recharging at least weekly. Also, overall battery life in such applications is typically short, so ongoing maintenance becomes a factor.

Even when a power source is nearby, it may be necessary to tear up roads, sidewalks, and landscapes to run wiring for an A/C connection. An A/C hookup may also require installing a meter to measure the amount of energy used.

Advances in photovoltaic technology have helped to increase the popularity of solar-powered displays, which eliminate the need for meters or power runs. But beware of a “one-size-fits-all” solution that could leave the sign inoperable during critical winter months.

The more energy the sign requires to operate, the bigger solar panel you'll need. Design features and the efficiency of individual components can make the difference between a sign that draws 10 W of power and one that draws 100 W. That can have a significant impact on the size or number — and hence the cost — of solar panels needed. If power consumption information isn't included in the product specifications, ask the manufacturer.

The specific environment where the sign is to be used also influences the size and number of solar panels required. The average sunlight for your region must be calculated. The specific location must also be examined for overhanging trees, roofs or other obstructions that can affect the panels' efficiency.

Calculating all of these factors may seem daunting, but it should be a straightforward process for any reputable dealer. Solar-powered signs are viable in virtually all areas of the United States.

“Even here in Alaska, where we receive long periods of sunshine and darkness depending on the season, our solar panel signs combined with battery backup power are used year-round,” says Michael Cobbold, safety manager and sustainability coordinator for Denali National Park, Alaska. “Our calculations showed that the technology we needed to employ solar power was still more cost-effective than it would have been to run a hard-wired connection to A/C power.”


Some models collect information regarding average traffic speeds, the number of passing cars, and the number of cars exceeding the posted limit. The data may be used to assess the need for traffic-calming enforcement and to evaluate the effectiveness of the radar speed display.