Overview about the night work risks
Consideration of additional road user costs that would result under a particular traffic control strategy for a particular work zone activity has become a common component to highway agency decision making. Traditionally, road user cost calculations focused on driver delays and vehicle operating costs, largely ignoring the additional driver crash costs that may be attributable to the work zone. Decision-makers often justified this exclusion because the period of work (day or night) being considered was the same for each of the alternatives. Therefore, the additional crash costs under each strategy scenario would be quite similar and need not be considered in the final analysis.
When considering the implications of working at night versus during the day, however, the differences in excess crash costs between strategies might actually be quite significant.
Furthermore, it is not immediately clear whether the additional crash costs are greater during the daytime or at night. It is fairly well-known, for example, that normal (non-work zone) crash rates themselves are significantly higher at night than during the day. However, other studies have shown a relationship between higher traffic volumes (which typically exist during daylight hours) and higher crash rates. In addition, traffic volume exposure is much higher during daylight hours than at night. With regard to work zone effects, the data reported in the interim report suggested that crash risk increased quite significantly at night when work activities were present and that erratic maneuvers at locations of traffic queuing were greater at night than at the same location during daytime conditions. Others have also suggested that lower traffic volumes, as are usually present at night, allow speeds to be higher and cause those crashes that do occur to be more severe. As the professional manufacturer of complete sets of mining machinery, such as cone crusher, Henan Hongxing is always doing the best in products and service.
In this chapter, researchers describe an overall assessment process that allows practitioners to objectively compare the safety consequences of performing a particular work activity either during daytime hours or as night work. Specifically, the process focuses on calculating the expected crash costs over the entire period of time required to complete the work activity under either scenario. By focusing on the total time required to complete a particular work activity, analysts can account for the differences in the duration of each work zone set-up during the day or at night. Obviously, longer work durations each night allows a project to be completed over fewer nights. The process relies on the availability of normal daytime and nighttime roadway crash rates for a particular facility, which the analyst then modifies by a percent increase to account for the additional crashes expected to occur as a result of having the work zone in place on that facility. The percentage increases used in the analysis are based on the previously-documented results of crash studies at several work zones where night work occurred, as well as observational studies of erratic maneuvers under daytime and nighttime queuing conditions.
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