美国养护工区特征分析

over one direction of a six lane freeway. Collectively, this capacity loss has ranged

between 5,000-5,300 miles of freeway in the summer and roughly 2,000-3,000 miles in the winter snapshots (Table 3).

Delay

No estimate of road user delay was generated from snapshot data. Delay data,

particularly quantitative estimates of delay, are extremely rare (5-6%), and cannot be used to accurately characterize delay. Although capacity loss can be estimated, without data on distributions of travel demand, alternative routes, and other data, a defensible estimate of delay could not be calculated from these measures.

KEY FINDINGS AND CONCLUSIONS

This section presents a summary of key findings from across the five snapshot studies and discusses some conclusions that can be drawn from the findings.

Key Findings

Analysis of data obtained from the state web resources contained enough detail to support During peak mid-day hours, there are 6,500-7,200 work zones covering 20-27% of the NHS has a work zone in the summer peak construction season.

Nationwide, off-peak (winter) work zone activity declines by more than half, with 2,000-3,000 work zones covering 7-8% of the NHS. About one-third of work zones with lane closures occur primarily at night.

The most likely hours of the day for a lane closure is 9-11 AM (roughly two-thirds of all work zones), the least likely is 6-7 PM (one quarter of work zones). The loss of nationwide capacity each day during the summer construction season on the NHS is about180 million vehicles – and losses in the peak hour equivalent

to the carrying capacity of over 5,000 miles of a six-lane freeway (one direction). The vast majority (80-90%) of work zone descriptions contain information on project purpose and duration, most (50-65%) report lane closures by time of day

and number of lanes closed, few (5-13%) provide delay advisories.

In comparison to a companion study of paper records of work zone activity in five DOT districts [9], it is clear that work zones posted to the web tend to be part of

the largest, most-visible projects in the state. Although the sample set of work

zones where the two studies had direct overlap was too small to analyze in any

depth, it is clear that work zones posted to websites tended to have somewhat

different attributes (most notably longer project durations).