Safety Evaluation of Profiled Thermoplastic Pavement Markings

Chapter 2. Objective

This research examined the safety impacts of using profiled thermoplastic pavement markings in Florida and South Carolina in comparison with more conventional markings, including a flat-line thermoplastic product. The objective was to estimate the safety effectiveness of this strategy as measured by crash frequency. Intersection-related, snow/slush/ice, and animal crashes were excluded. The following target crash types were considered:

• Total crashes (all types and severities combined).
  
  
• Injury crashes (K, A, B, and C injuries on the KABCO scale, where K is fatal injury, A is incapacitating injury, B is non-incapacitating injury, C is possible injury, and O is property damage only).
  
  
• Run-off-road (ROR) crashes (all severities combined).
  
  
• Head-on crashes (all severities combined).
  
  
• Sideswipe-opposite-direction crashes (all severities combined).
  
  
• Sideswipe-same-direction crashes (all severities combined).
  
  
• Wet-road crashes (all types and severities combined).
  
  
• Nighttime crashes (all types and severities combined).
  
  
• Nighttime wet-road crashes (all types and severities combined).

A further objective was to investigate ways in which effects might vary, such as the following:

• By roadway type.
  
  
• By level of traffic volumes.
  
  
• By posted speed limit.
  
  
• By shoulder width.
  
  
• By lane width.
  
  
• By the site-specific expected crash frequency prior to treatment.
  
  
• By the overall effect, measured by the economic costs of crashes by crash type and severity.

The evaluation of overall effectiveness included consideration of the installation costs and crash savings in terms of the B/C ratio.

Meeting these objectives placed some special requirements on the data collection and analysis tasks, including the following:

• Selecting a large enough sample size to detect, with statistical significance, what may be small changes in safety for some crash types.
  
  
• Identifying appropriate untreated reference sites.
  
  
• Properly accounting for changes in safety due to changes in traffic volume and other nontreatment factors.
  
  
• Pooling data from multiple jurisdictions to improve reliability of the results and to facilitate broader applicability of the products of the research.