THE HUMAN ELEMENT IN TRAFFIC SAFETY

Much is said about the competence of typical drivers. Although they are the butt of many jokes and can be a pain in the neck to fellow motorists, how much of this negative perception is justified?
 
   How competent are regular drivers in managing their automobiles? 

   How safe are we on the nation’s highways?

 Let’s take a look at some scientific facts.

TRAFFIC SPEED AND FATALITY RATES

The following chart shows the relationship between the fatality rate and speed limits in the state of Utah and, except for the numerical values, this chart is representative of conditions in virtually all other states.

Fatality Data Provided by National Highway Traffic Safety Administration
Normal Traffic Speed Increases by Approximately 0.5mph per Year

FATALITY RATES TREND STEADILY DOWNWARD

The Utah traffic fatality rate has trended steadily downward over the last thirty years in the face of ever-increasing traffic speeds.

1.  The data show a steady decline over this period although normal freeway speeds have increased at approximately 0.5mph per year.

2.  The speed at the upper 15% percentile of the normal traffic speed has increased from approximately 70mph in 1975 to approximately 85mph in 2004. 

Except for erratic behavior during the years immediately after 1974 when the 55mph National Speed Limit was imposed, this data strongly indicates that there is no direct relationship between speed limits and traffic fatality rates in Utah. The experience of other states is similar.

MODERN TECHNOLOGY ALLOWS MOTORISTS TO DRIVE SAFELY AT HIGHER SPEEDS

Technological improvements in highway and automobile design have allowed motorists to travel safely at ever faster speeds. In many states the normal, safe speed of traffic has increased to approximately 10mph faster than many posted speed limits while fatality rates continue to decline. 

MOTORISTS ADJUST SPEED TO SAFE, COMFORTABLE LEVELS

Less skillful drivers, motorists driving less capable vehicles, or driving during poor weather conditions, automatically adjust their speed to a comfortable level for the existing conditions. If they see a speed limit that they believe is too high for current conditions, they drive more slowly.

So, why is there so much confusion in managing this very important traffic safety component?

SPEED LIMIT MYTHS

Two speed limit myths prevail throughout the United States: 

1. Speed limits are necessary to assure that traffic flows at safe speeds.

2. Most motorists will always drive faster than posted speed limits. 

There is much evidence that these myths have a virtual stranglehold on traffic safety action groups and government agencies authorized to set speed limits. 

SPEED LIMITS DO NOT AFFECT SPEED OF TRAFFIC

The already-mentioned landmark study completed in 1992 by the Federal Highway Administration should have laid the above mentioned myths to rest when it determined that there is no significant relationship between posted speed limits and the speed of traffic. This study and others clearly show that: 

1.  Increasing speed limits does not produce faster traffic speeds—With very few exceptions, motorists select safe, “reasonable and prudent” speeds at which they are comfortable. If they read a speed limit that  they believe is too fast, they drive more slowly.

2.  Lowering speed limits does not produce slower traffic speeds—When motorists read a speed limit sign that they believe is too slow, they drive at a faster speed that they consider comfortable and safe.

3.  Speed limits are basically irrelevant—Drivers do not refer to them when choosing the speed at which they drive. 

PUBLIC INDIFFERENCE

Many motorists accept speeding citations as an unpleasant, almost unavoidable, fact of life. Although they may know that they were driving safely when they were cited for speeding, rather than spend the considerable time and money to contest a speeding ticket, they simply pay up and hope that their luck is better in the future.

INAPPROPRIATE GOVERNMENT ACTION

Then there are government officials who are confronted by neighborhood groups expressing concern that traffic in their neighborhoods is too fast. These officials may react by lowering speed limits in the misguided belief that traffic will flow more slowly. While this response may mollify a few citizens, it does not solve their problem as traffic continues at the same speed as before.

Unfortunately, there are also indifferent or uninformed government officials who either do not know or do not acknowledge that setting proper speed limits is a complex and exacting process that should only be done by qualified traffic engineers.

The next page describes how fair, valid speed limits are to be created.