Does poor road condition increase crashes?

| David Levinson

In a region well known for its severe weather, maintaining pavements to meet high standards remains a challenge. Changes in weather states (such as the freeze-thaw cycle) leads to distresses in the pavement materials. There exist claims that poor pavement quality reduces the ability of roads to drain and reduces the ability of vehicles to resist skidding, and is thus associated with more crashes. In order to improve road safety, several pavement maintenance treatments are carried out, such as “rout and seal cracks” and “hot-mix patching” for improving pavement roughness and distress (Tighe et al., 2000). Others have found that crash rate depends on the pavement type and pavement condition. Crash rate of tined pavement sites is larger than the rate of ground pavement sites. When the pavement condition is wet or icy, crashes are more likely than under dry conditions (Drakopoulos et al., 1998). , When the pavement condition is poor, severe crashes are more likely, but when the pavement condition is very poor, severe crashes are less likely to occur than poor pavement conditions (Li et al., 2013). In accident rate estimation models, the results indicate that most important independent variable is “AADT”, and “geometric design” (lane width and access control) and “pavement condition” (friction, serviceability index, and pavement type) are also important variables (Karlaftis and Golias, 2002). Our research proposes to statistically test such claims of a relationship between incident number and road quality, while controlling for traffic data (AADT and percent truck), segment length, crash conditions (date, road characteristics, and road surface), and pavement type. To investigate the relationship, we combine data from various sources. We then conduct a statistical analysis for ascertaining the effects of good road quality on incident number and severity. This paper describes the data, methods, hypotheses, and results in turn.

One thought on “Does poor road condition increase crashes?”

  1. David,
    In the early 1970s I worked for RAND in NYC. I was hired by the NYC transportation department to analyze the effect of street conditions on traffic accidents. The department hoped to show that poor road conditions were unsafe and thus the city should receive increased financial aid from the state.

    The city collected an excellent data base: direct observations of road conditions (numbers of potholes and patches by block and smoothness measures) for a large sample of blocks in Manhattan and Brooklyn. These were for local streets rather than avenues. We found that the worse roads were the safest — very strong statistical results. In sum, the poor roads were so bad that cars had to slow down and thus had very few reported crashes. We had no data on other damage to cars — shock absorbers, tires etc. The city was not pleased and the data were never published.

    A second finding, was that streets in Brooklyn were in much better shape than in Manhattan. The DOT speculated that this might be due in part because Brooklyn originally mandated that residents of each street had to maintain the roads in front of their houses. This is no longer true of course, but the better original road conditions still carried over.

    Dick Mudge

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