Table of Contents

3. Data Collection

3.1 Methods

Data for this effort was collected from web-based resources linked to the National Traffic and Road Closure Information page (www.fhwa.dot.gov/trafficinfo/). Of the 50 state and other resources listed, data on individual roadway projects and their associated work zones in 13 states were electronically captured and downloaded over the two-week period 25 June - 10 July 2001.

The selected states (Arizona, Idaho, Indiana, Kansas, Kentucky, Montana, Nebraska, Nevada, Oregon, Tennessee, Utah, Virginia, Washington) are shown in Figure 1 with the number of work zones posted by state. In total, these states posted information on 789 work zones on the reviewed websites. The 13 states used for this study were not randomly selected - instead, the states were selected based on the number of work zones described and the amount of detail provided for each work zone. The data were organized differently from state to state, and in many cases descriptions provided in text form, so an analyst was required to inspect and code each record.

 

Figure 1. Number of Work Zones Reported by State on Web-Based Resources
Figure 1. Number of Work Zones Reported by State on Web-Based Resources [D]

The categories of data captured and coded from each web record were:

Not all data elements were available in each web record. For example, 619 of the 789 work zones (78%) reported the purpose of the project. Also, 175 of the 789 work zones (22%) reported activity or lane closures by time of day. Table 2 summarizes the reporting frequency of each data element for all 789 work zone records.

Table 2. Data Element Reporting Frequency by State
empty cell empty cell Percent (%) of Work Zones Reporting:
State Number of Work Zones Reported Length Project Duration Number of Lanes Closed Closure Duration Delay Purpose Cost
Arizona 68 57 94 43 96 13 47 0
Idaho 44 0 95 64 9 2 100 36
Indiana 137 5 99 16 2 0 93 0
Kansas 140 8 100 4 0 95 94 0
Kentucky 49 78 2 63 0 43 4 0
Montana 90 6 0 40 1 0 96 3
Nebraska 8 25 100 0 0 0 38 0
Nevada 33 0 45 36 79 3 39 0
Oregon 21 62 57 67 48 5 57 0
Tennessee 35 43 0 94 14 17 86 0
Utah 39 13 95 51 36 33 92 0
Virginia 47 11 94 38 9 26 64 0
Washington 78 3 83 58 62 6 91 15
Average 61 18 71 37 22 26 78 4

 

Each state reports work zone data independently. The state-by-state data in Table 2 shows that some data elements appear more frequently in some states than in others. One key observation is that some states report on many work zones but provide fewer data elements (e.g., Indiana) while others report on fewer work zones but provide more data elements (e.g., Washington). A second observation is that no state provides all data elements for all work zones.

Table 2 shows that attributes of roadwork that are set early in the planning process and are unlikely to change are more frequently reported. These data elements include such basic attributes as project duration and purpose. Less frequently reported elements are work zone attributes that are difficult to predict in advance or those that may change on a daily, weekly or monthly basis. These data elements include the work zone length, the number of lanes to be closed, and the time-of-day when lane closures occur.

Uncertainty in the reporting of some data elements is also reflected in increasing ambiguity. In the case of lane closures, it is 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. Expected delay, particularly quantitative estimates of delay, is very infrequently 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. The data elements included on websites also reflects that the target audience for these websites ranges from roadwork contractors and DOT personnel to the traveling public. In many cases data elements that may be of more interest to contractors and DOT personnel (e.g., project location and purpose) are easier to estimate and are frequently reported. Data elements of interest to the traveler (e.g., quantitative estimates of delay) are harder to estimate and are less frequently reported.

The web-based resources report almost exclusively on the facilities that reflect state DOT responsibilities: interstates, US highways, and state routes. Table 3 shows that although some local street work is reported on some websites, the focus of the web-based resources examined is on roadwork contracted and overseen by the state DOT.

Clearly, additional roadwork also occurs within the boundaries of the states considered here. We do not know how many work zones are set up by the state but not reported on the website, nor can we infer a level of work zone activity overseen at the county or local level. Therefore, the data collected in this study from state websites was a subset and should not be construed as a completely representative illustration of all maintenance and construction activity across the nation.

Table 3. Facility Type Reported With Work Zone by State
empty cell empty cell Percent (%) of Reported Work Zones
State Number of Work Zones Reported Interstate/US Hwy State Highway Local
Arizona 68 57 41 1
Idaho 44 68 32 0
Indiana 137 55 46 1
Kansas 140 74 26 0
Kentucky 49 61 43 0
Montana 90 61 38 1
Nebraska 8 50 50 0
Nevada 33 58 15 21
Oregon 21 62 24 0
Tennessee 35 97 0 0
Utah 39 36 23 36
Virginia 47 60 40 0
Washington 78 27 67 4
Average 61 59 37 3

3.2 Other Web Resources for Work Zone Information

In addition to the web-based resources used for data collection in this study, several of the states also participate in partnerships with various federal, state and local bodies. The partnerships agree to provide regional lane closure information through contracted Web services. Although we did not utilize these resources for this study, we note them here for completeness. For example Ohio, Kentucky, Indiana and the FHWA are in a partnership to provide support for the Advanced Regional Traffic Interactive Management & Information System (ARTIMIS) (www.artimis.org). This web site reports information similar to that collected in this study. An independent contractor operates the system. Likewise, the I-95 C orridor Coalition sponsors a web site (www.i95coalition.org/traveler_info.htm) that provides information on lane closings, bottlenecks and upcoming events throughout the I-95 corridor. Some information is posted weekly. Other information is provided as a yearly forecast of expected traffic disruptions. This site also provides information on broader policy issues of interest to this group. These issues include electronic payment systems, commercial vehicle operations and intermodal transfer of people and goods.

Some states have a few projects that have project specific websites, such as Virginia's Springfield Interchange project (www.springfieldinterchange.com.) These resources are typically maintained by a project contractor or consultant, and feature various combinations of: project histories, newsletters, maps, safety information, alternative modes, technical information, media contact information, and frequently asked question (FAQ) support. Real-time or predicted delays through the work zone are seldom reported for these sites. This information is not typically captured during the construction phase of a project. These sites offer additional detail on work zone operations beyond the information presented in the statewide resources used in this study. However, there are too few of these sites to support statewide or nationwide sampling.

Some private sector websites also post information on work zones. For example, MapQuest (www.mapquest.com/traffic/main.adp) provides a summary of work zone information by location for many large metropolitan areas (64 in late 2001). However, these private sector sites generally provide less detail on work zone activity than public sector resources.

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