It is unlikely that this level of increase can be explained by an increase in work zone activity and traffic exposure. However, the use of an explicit variable on the form will not solve the entire accident data problem. However, based on limited investigation of four selected work zones, as many as 77 percent of crashes that did occur within the four zones were not coded as work zone accidents. One likely explanation for this is that a police of ficer may interpret the work zone accident variable to only apply when construction activity was present or had an influence on the accident. An explicit data element regarding work zones on police accident report forms and clear definitions of work zone-related data elements are necessary if estimates of the magnitude of the work zone accident problem are to be improved.
Questions still remain regarding the safety of work zones.
Past studies about work zone safety were mostly based on very limited data. Very few studies attempted to explicitly consider exposure to work zone activities or to develop work zone accident rates that account for differences in exposure. A key need is to determine an appropriate exposure measure to calculate the work zone crash rate. Example of data elements for work zone accident in an accident report form. M.P. Fenner, E.E. McAdams, and D.J. Mercer, Assessment of Michigan State Trunkline Construction Zone Accident Data, Report No.