Roadside Signs: Research Shows What Works Best

Roadside Signs: Research Shows What Works Best

Bob's Garden Center roadside signAny retailer who has ever erected or made changes to a roadside sign for their business understands the biggest challenge often doesn’t involve choosing the right wording or colors. More likely, it’s dealing with your local zoning board.

If zoning laws for roadside signs seem random to you, there’s a fair chance you’re right. Until 2011, zoning boards did not have solid research to rely on when developing their rules.


Safety should be a large component of zoning laws, but without research, boards can’t know which heights and sizes cause less confusion and therefore fewer driver mistakes.

But that changed when the United States Sign Council (USSC) published its findings about how roadside signs should be designed. The non-profit research and trade organization, which has acted as an advisory group for zoning boards nationwide, collected research from different government agencies and several universities to create a model code for store signs. Model codes are created every 10 years, and the 2011 report is the first model code with research to back it up.

New Guidelines Cover Every Facet

Dismayed at the lack of research available, the USSC Foundation teamed up with traffic engineers, “human factor” researchers, universities and public transportation departments to fully assess safety and legibility of roadside signs.

As you would expect when lab-coat types get together, no detail was deemed too insignificant. Eye movements, road conditions, weather, fonts, sign dimensions and even the drivers on the street were all examined closely over a 15-year span in multiple studies.

The synopsis of all this work was compiled into a 44-page report with the dry-but-comprehensive title, “On-Premise Signs Guideline Standards Research Based Approach to: Sign Size, Sign Legibility, Sign Height.”

The study examines a number of different issues, including:

  • Viewer reaction time
  • Viewer reaction distance
  • Letter height
  • Copy area
  • Negative space

Viewer Reaction Time

Researchers measured how long and how often drivers looked at signs in dozens of scenarios, including how long it takes to notice the sign and distinguish it from its surroundings.

They watched an older driver on a simple two-lane road with little traffic driving 30 mph, a 20-something driver in the left lane on a more challenging road driving 40 mph, and so on.

The group learned a couple things that retailers should know. First, the view from the driver’s seat is limited. On average, drivers will not look any further than 10 degrees away from directly in front of them. That means your sign should be as close to the roadside as your property lines and zoning regulations allow.

Detection time is longer than you think. Just noticing the sign is there takes about one-half to a full second.

Comprehending what’s on the sign relies on its setting and its content. Researchers figured out that it takes about a half second per five-letter word to understand what a sign says, or one-tenth of a second per letter or symbol. The more letters and symbols, the longer it takes for a driver to read the sign.

View Reaction Distance

This portion of the research examines what happens once a driver understands the sign and wants to pull into the parking lot. How much distance do they have to maneuver the car?

Being researchers, the team created a formula to calculate exactly how long (and therefore how far) it takes for the driver to detect and comprehend the sign, and then react to maneuver the car. In simple conditions (an uncomplicated two-lane road, with few distractions, for example), that time is about four seconds. In a town or city commercial area with traffic under 35 mph, it’s five seconds, and above 35 mph, it’s six seconds.

The formula for calculating distance is a two step process. First you need to figure out the feet per second that drivers are traveling. To do that, multiply the miles per hour by 1.47.

Next, multiply the reaction time above (say, five seconds for the town commercial district under 35 mph) by the feet per second. This will give you your distance in feet.

In this example, it takes 257 feet for a driver traveling 35 mph to react to a sign in five seconds. With this in mind, you can see the importance of having a sign large and clear enough to notice well in advance of the entrance to your parking lot.

Letter Height

The study determined how many inches in letter height it takes per distance to be legible to drivers. One finding is that signs with all capital letters need to be 15 percent taller than those with upper and lower case letters. For example, MY GARDEN CENTER would need to be 15 percent taller than My Garden Center.

Copy Area And Negative Space

The copy area of your sign is the space taken up by the words and images. The negative space is all the area left. The research found that negative space should never be less than 60 percent of the sign if you want it be easily comprehended.

Keep these best practices in mind the next time you’re asking permission for significant changes to your roadside signage, or even just finding ways to improve your existing signs. It can mean more customers in your parking lot and in your garden center.

To read this report and several other related reported, go to