The Copernican Revolution: A New Model for Highway Safety

In the 15^th century, scholars believed that the earth was the center of the universe and the sun and the other planets rotated around the earth. 

This seemed logical – they lived on the earth and from their vantage point, the sun appeared to be moving, not the earth.  Nicolaus Copernicus saw things from a different perspective.  Copernicus contended that the sun was the center of the universe, not the earth.  His heliocentric model, demonstrated that the observed motions of the planets can be explained without putting the Earth stationary in the center of the universe. Heliocentrism represents a starting point in modern astronomy and a revolution in scientific observations. 

Highway safety is now undergoing a Copernican Revolution of sorts.    For years, highway safety management has centered on crash data.  This seemed logical – the goal of highway safety efforts are to eliminate crashes so crash data should be the starting point.  Engineers and others responsible for highway safety have used crash databases to find locations with high crashes and focused improvement efforts on those locations. 

However, just because an intersection or segment of roadway doesn’t have a reported crash in a database, doesn’t mean that the location is safe.   Crash data are incomplete as many crashes go unreported, patterns are unstable, and location accuracy is often unreliable. 

Just as the earth doesn’t need to be the center of the universe to be important to the human race, crash data doesn’t have to be the center of highway safety management to be important to improving safety.  In highway safety, the universe can have another center.

The Federal Highway Administration is currently conducting a demonstration using roadway inventories as the center of highway safety management.  Roadway inventories are much larger and more robust than crash databases.  A good roadway inventory has information on every segment and intersection in a jurisdiction linked through a common location referencing system, whereas a crash database only includes locations with crashes.  Roadway inventories are also expandable.  That is, as more about a particular location is known or as conditions change, the roadway inventory can expanded or updated.

In this highway safety heliocentric model, the larger, more robust roadway inventory is the sun and the crash database is the earth.  Other relevant databases such as traffic volumes, safety improvement databases, pavement databases, and sign inventories can be considered the planets.  Together with the crash database, these databases can be linked to the roadway inventory for use the same way that Mars, Mercury, Venus, and the Earth rotate around the sun in a solar system. 

This linked solar system of heliocentric data, or Management Information System (MIS), presents numerous opportunities to expand highway safety improvement efforts beyond simple identification and diagnosis of safety by frequency of crashes.  Reported crashes can be combined with traffic volumes to consider exposure in detailed reviews by location type (e.g., all 3-leg signalized intersections).  As more planets (databases) are linked together in the solar system (MIS), more sophisticated analysis can be conducted, presenting numerous opportunities to improve highway safety.  For example, planned paving projects can be reviewed to find segments with run off the road crashes that could be improved by adding rumble strips as part of the repaving.  Unsignalized intersections with close proximity to power can be identified to find locations where adding lighting to reduce nighttime intersection crashes is cost-effective.  The location of horizontal curves can be compared to roadway departure crashes and appropriate signing.  The possibilities, like the universe, are seemingly endless.

Copernicus didn’t get to experience the advances that resulted from his model; it wasn’t until 200 years after his death that heliocentrism was widely accepted.  My hope is that the highway safety community embraces the heliocentric model for highway safety much faster. 

To learn more about the use of roadway inventory data to improve highway safety, please visit the FHWA MIRE website at www.mireinfo.org.