5. Implications and Conclusions
The web-based resources examined in this study are an attempt by the states to keep a variety of audiences informed, including the traveling public. When accessing one of these sites, a user can fairly consistently find an approximate roadway location of a work zone, the purpose of the closure, and what type of capacity loss can be expected (e.g., shoulder work or number of lanes closed). From a construction and maintenance standpoint, this is readily available information that changes the least throughout the project. However, there is additional information that is critical for a traveler to know. Information such as lane closure beginning and end time, dates, and expected delay are critical decision factors for a motorist. These data however are far less frequently reported. One possible explanation for this is that this data changes more frequently. For project personnel, coordinating and scheduling the many resources for a lane closure and associated work can be difficult, with dates and times changing often. It is hard to predict months or weeks in advance when certain lane closures may occur. Detailed information almost needs to be reported within hours of a lane closure. Depending on how sophisticated the linkage between the work zone personnel and the web resource, this information may not be posted in time to be useful. The posting of this critical data is limited by the difficulty in obtaining accurate information and making reliable estimates of delay well in advance of the actual lane closure.
Further, many of the critical data elements needed for travelers are not critical to the completion of the roadwork. Measurement of delay, for example, is rarely required of construction and maintenance personnel. Qualitative statements of delay (major or minor) may be posted, most often based on an educated guess or manual count.
Ideally, work zone web resources targeted for traveler use would report the following information on work zone activity:
- Start and end dates
- Lane closures or other roadway capacity impacts by date and time of day
- Location of work zone
- Number of lanes closed
- Estimated delay by direction of approach and time-of-day.
Overall, the web-based resources identified during the snapshot study provide enough detailed data to allow for rough estimation of several national-level measures related to the number, prevalence and capacity impacts of work zones. However, data acquired from these websites are unlikely to be completely representative of all work zones, since, until now, the websites primarily focus on larger projects under state DOT jurisdiction. In addition, there is significant ambiguity in the reporting of several data elements, including project/work zone duration and hours of lane closure or work zone activity. Therefore, the national estimates should be considered indicative rather than authoritative figures.
Based on data collected from a subset of 13 state web resources linked to the Federal Road Closure Information page, we estimated that there were 3,110 work zones on the National Highway System over a two-week period during the peak summer roadwork season. Further, these work zones covered 20,876 miles of NHS roadway, representing 12.8% of the 163,734 miles of roadway designated as part of the NHS. Based on lane closure data, we estimated that the work zones on the NHS result in a loss of over 60 million vehicles of capacity per day. During the hour when roadwork most frequently impacted capacity (between 9AM and 10AM), the collective impact of work zones on the NHS was estimated at 2,672 lane-miles of freeway, or roughly the carrying capacity associated with one direction (three lanes) of a six-lane interstate connecting Washington, DC to St. Louis, MO. National estimates of delay and productivity impacts could not be determined from the data available on the state web resources.
Of the work zones examined, 58% were active or had lane closures primarily during daylight hours, 33% were primarily night work, and 9% were active nearly around the clock. The average work zone had lane closures for 11 hours a day and occupied 6.8 miles of roadway for an average of 125 days.
At least for these measures, compiling data from web-based resources gives federal policy makers some insight into the level of work zone activity at the national level. Data acquisition from the websites is relatively straightforward and can be automated to reduce costs of a potential monitoring program. However, since the data reported is inconsistent and somewhat ambiguous, the interpretation and coding of the data is less easily automated and more costly. Some standardization for basic data elements, or failing that, more careful description of data posted to the websites would assist in the collection and calculation of national-level statistics. Any monitoring program using these data resources must also consider that the tracking of national-level measures over time may also be confounded to some degree by a simple increase in reporting of work zone data to the web. For example, when a state DOT doubles the number of work zones reported on its website, it may reflect a statewide initiative to increase reporting, rather than a doubling of the number of actual work zones on the roadway system.
