美国养护工区特征分析

WORK ZONE WEBSITES: DATA ELEMENTS AND TRENDS

Typical data elements that were identified for each work zone include:

Location. This element typically references a roadway by name and indicates an approximate location by referencing a nearby

exit, mile post marker, or town.

Purpose.Project purpose is often described in detail, (e.g., “erosion control”).

Project Duration.Project start and end dates are typical data elements. Duration is computed as the difference in days between

these dates.

Length.The length of a work zone is most often expressed using mile post designations (e.g., “between MP 12.4 and 18.1”) Lane Closure ne closures are identified for work zones by day of week and time of day. The number of lanes closed or other

capacity impacts are also reported here.

Delay.Sometimes an advisory about potential delays are posted, and in rare cases an estimate in minutes of delay is posted. Cost.Total project costs are sometimes included.

Some data elements are reportedmore frequently than others. Every work zone record identified had some sort of location entry. Excluding the 2001 pilot study, the vast majority (86-90%) of work zone descriptions contain information on project duration, most (51-62%) report lane closures by time of day and number of lanes closed, while few (5-13%) provide delay advisories. Table 1 presents our key data elements and their frequency of reporting in each of our Snapshot analyses, including the 2001 pilot study.Some elements frequently reported while others are rarely reported. For example, expected delay, particularly quantitative estimates of delay, arerarely reported. The dearth in delay reporting reflects the fact that delays are not typically estimated in detail prior to the start of roadwork and are not typically monitored precisely once roadwork is underway. It is also clear that different state websites have different target audiences ranging from roadwork contractors and state personnel to the traveling public. In many cases data elements of interest to contractors and state personnel (e.g., project location and purpose) are known in advance of the actual roadwork, do not change, and are

frequently reported. Data elements of interest to the traveler (e.g., lane closure schedules or quantitative estimates of delay) can change from day-to-day or minute-to-minute, are harder to estimate, and are less frequently reported.

Discerning the precise meaning of some data elements is complicated by ambiguities and inconsistencies among states and within states. The snapshot study approach in such cases is to have a clear, consistent coding policy to guide the analyst. For example, when states report times of day with lane closures in a work zone, it is frequently unclear whether the intervals reported are the times of day when a traveler may encounter lane closures or times of day when a traveler is certain to encounter a lane closure. In the