1. HSIS Annual Meeting, 10/2006 NCHRP 17-30: Traffic Safety Evaluation of Nighttime and Daytime Work Zones Raghavan Srinivasan Forrest Council

2. HSIS Annual Meeting, 10/2006 Background More and more agencies are doing roadway work at night Nighttime travel is associated with: –Lower traffic volumes, but higher speeds –Reduced visibility –Potentially more drowsy and impaired drivers

3. HSIS Annual Meeting, 10/2006 Objectives Determine the nature of traffic crashes in daytime and nighttime work zones Determine the trade-off between daytime and nighttime work for the same type of work zone Develop management practices to promote safety and mobility in work zones Develop work zone reporting recommendations to improve data collection for work zone crashes

4. HSIS Annual Meeting, 10/2006 Project Team Lead agency: Texas Transportation Institute (Gerald Ullman is the PI) Subcontractors –HSRC (Raghavan Srinivasan) –VHB (Forrest Council) –James Bryden (Consultant from NY) Project started in May 2004

5. HSIS Annual Meeting, 10/2006 Overview of Proposed Approach Basic question: whether work performed at a particular location would produce fewer (or less severe crashes) as a daytime or nighttime work zone Analysis approach: –EB before-during analysis using matched comparison (non work-zone) group with similar AADT and geometry –Compare crashes at the times and days when work activity was present to similar days and times before work zone was initiated –Examine crash costs (combining severity and frequency)

6. HSIS Annual Meeting, 10/2006 Work Zone Data Elements Work zone lengths Hours of activity when workers are present Work Zone Type –Pavement repair and rehabilitation (short-term lane closure) –Major reconstruction and widening (long-term lane closure) Duration of work zones Length and duration of lane closures Purpose of the work zone Traffic volumes Traffic control plans

7. HSIS Annual Meeting, 10/2006 States being Targeted HSIS States –North Carolina –Washington (Northwest & Olympic region) –Ohio –California New York –Have a separate database for work zone crashes –Supervising engineer has prime responsibility for reporting the crash –One sentence narrative is provided for each crash. Can be used to determine if it was work-zone related.

8. HSIS Annual Meeting, 10/2006 Identifying Construction Projects Contacted Construction Divisions –List of projects completed in the last few years –Determine if they are night/day/day&night projects by contacting resident engineers –Ensure that they were on limited access facilities –Determine work zone type –Short listed projects for detailed review

9. HSIS Annual Meeting, 10/2006 Extracted Project Diaries Extracted project diaries and manually reviewed them –Very time consuming task –Reviewed project diaries for a total of about 10,000 days in NC; probably a similar number in the other 3 States –Some of the information from OH was typed –Recorded information on lane closures and times of work –Reviewed traffic control plans

10. HSIS Annual Meeting, 10/2006 Extracting Needed Data In the process of extracting crash and roadway inventory data –‘Before’ and ‘during’ at the work zone sites –‘Before’ and ‘during’ at the comparison sites Some comparison sites may have had work zones In the process of obtaining data on hourly volumes –From permanent count stations –Other short-term counts –Will have to use these to estimate work zone counts – both day counts and night counts Expected completion – May 2006

11. HSIS Annual Meeting, 10/2006 What We’ve Learned… Work zone safety studies are very difficult to conduct because of: –Shortage of historic, mileposted WZ location data – difficult to find and to link with other safety files –Lack of WZ traffic counts –Many short-term changes in traffic control –Critical data have to be manually extracted due to lack of computerized “journals” –Near-by comparison/reference sites may also have WZ during study period –Type of work differs by day/night –“Window of WZ effect” is difficult to define since queue length can vary But, very important to do, since we may see more nighttime work zones in the future