美国养护工区特征分析

and principal arterials, as well as connector roadways critical for defense or the

movement of goods between intermodal facilities.

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Project Length

In summer 2003, the average work zone length was 6.1 miles and the median length was

2.9 miles. A number of long work zones associated with paving work accounts for the difference between the average and median length values and has been observed

consistently in 2001 and 2002. As indicated in Table 2, work zone length has varied from

5.3-6.8 miles in the summer, and 3.8-4.5 miles in winter. The shorter winter work zone length is related to a drop in paving work in cold weather states.

Project Duration

Duration is one of the most widely reported statistics, with an average duration of 98 daysin summer 2003 (about 3 months) and a median of 16 days (about 2.3weeks). This

reflects a consistent pattern where the average duration is higher than the median duration because of a number of multi-year projects. One trend that can be observed from Table 2 is the decline in average project duration from summer 2002 to summer 2003. One reason for this decline is the trend in state website reporting format away from a project-level perspective to a daily lane closure perspective. When a state adopts the daily lane closure perspective, often it is difficult to discern project duration, particularly for large, complex projects lasting more than one season.

Lane Closures by Time-of-Day

Roughly half of the records inspected reported the time of day when the work zone had lane closures that were in place or capacity reductions from work zones. Of these records, summertime lane closures averaged 11.0-11.9 hours per day over our five

snapshot studies in 2001-2003. On average, winter lane closures had somewhat shorter durations, averaging 9.0-10.7 hours per day.

This data was further stratified into three subgroups: Work zones with capacity impacts 18 or more hours per day, work zones active (or with lane closures) primarily at night, and work zones with capacity impacts primarily during daylight hours. Any work zone with a duration under 18 hours but more than 2.5 hours of work during presumed hours of darkness (10 PM – 5 AM) was designated as “nightwork.” All other roadwork with duration less than 18 hours per day was designated “daywork.” Roughly a quarter to a third of all roadwork meets our definition of “nightwork” in the summer. Nightwork is generally lower in the winter.

Lane closure data can also be arranged to show capacity impacts by time of day, broken down by 30-minute periods (illustrated in Figure 2 for summer 2003). Note that some work zones that are primarily nightwork can extend into the mid-morning hours.