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Safety Data and Analysis in Developing Emphasis Area Plans (2008)

Chapter: Section X - Reducing Crashes in Work Zones

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Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Page 83
Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Page 84
Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Page 85
Suggested Citation:"Section X - Reducing Crashes in Work Zones." National Academies of Sciences, Engineering, and Medicine. 2008. Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press. doi: 10.17226/14170.
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Page 85

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79 The FHWA rule on work zone safety and mobility (31) specifies that each agency “develop and implement system- atic procedures to assess work zone impacts in project development and to manage safety and mobility during project implementation.” This rule states that agencies “shall continually pursue improvement of work zone safety and mobility by analyzing work zone crash and operational data from multiple projects” (31). Strategies to reduce work zone accidents can cover a broad spectrum of the roadway system. Every freeway, rural road or city street will at sometime in its life cycle be in a work zone. These work zones can vary in duration from a 1-hour crack sealing location, to a complete reconstruction lasting months or years. Exposure of road users to work zones is extremely difficult to measure and has been the subject of several research projects. The work zone crash history is often similar to the crash experience of the roadway prior to work. It is recommended that the crash history of the roadway be reviewed as part of the work zone design process. While all crashes that occur during a work operation may be termed “work zone” crashes, it may be beneficial to examine other guides for reducing crashes in a specific area. For example, if there are a large number of single vehicle run-off-road crashes, the guide for reducing run-off-road crashes should be consulted. Many agencies specify that project engineers collect data on work zone crashes that occur on their projects. While this procedure ensures that project personnel are aware of crashes taking place on their project, and analyses of these crashes may supplement other analysis, they do not involve the crash records system and therefore are not discussed in this guide. In the FHWA rule on work zone safety and mobility the definition of work zone crash is as follows: Work zone crash means a traffic crash in which the first harm- ful event occurs within the boundaries of a work zone or on an approach to or exit from a work zone, resulting from an activity, behavior, or control related to the movement of the traffic units through the work zone. This includes crashes occurring on ap- proach to, exiting from or adjacent to work zone that are related to the work zone (31). Analysis of work zone crashes will be discussed in terms of the existence of three items or data files. 1. The existence of an item on the crash record that identi- fies the crash as a work zone crash. It is recommended that this work zone crash identifier be an explicit item that must be completed, if applicable, for each crash, rather than being one of many possible contributing circum- stances that might be noted in a field such as “roadway defects.” 2. A work zone or project file that lists the location and dates of various work zones. This file may only contain data on construction projects of long-term duration, or may also include short-term maintenance and utility work zones. 3. Computerized roadway inventory data including traffic count data that can be linked to the crash data by location of the crash. As discussed in Appendix 9 of A Guide for Reducing Work Zone Collisions (17), the Model Minimum Uniform Crash Criteria (MMUCC) recommends that four fields be collected on work zone crashes as follows: 1. Was the crash in or near the construction, maintenance, or utility work zone? If yes collect fields 2–4. 2. Location of the crash: a. Before the first work zone sign b. Advance warning area c. Transition area d. Activity area e. Termination area 3. Type of work zone: a. Lane Closure b. Lane shift/crossover S E C T I O N X Reducing Crashes in Work Zones

c. Work on shoulder or median d. Intermittent or moving work e. Other 4. Workers present? Crash reduction strategies in work zones must first of all be effective for the type of road being worked on. Crash reduction factors are not known for work zone crash reduction strategies, but can be estimated for no-work zone conditions. For exam- ple, if shoulder rumble strips have a 0.80 CRF outside of work zones (i.e., result in a 20 percent reduction in run-off-road crashes), then a rough estimate of their effectiveness in work zones is the same 0.80 CRF. Different levels of analysis can be undertaken depending on the types of crash, roadway, and work zone information available. Four levels of analysis are discussed based on data availability as follows: • Level 1 Analysis – crash data include a work zone flag/ variable, a complete highway inventory is available, and the location and date of all work zones from construction, maintenance and permits (utility) sections are available to link with the highway inventory. • Level 2 Analysis – crash data include a work zone flag/ variable and a roadway inventory is available, but there is no work zone file. • Level 3 Analysis – crash data include a work zone flag/ variable, but there is no work zone file or highway inventory. • Level 4 Analysis – crash data do not include a specific variable indicating a work zone crash, but other fields such a traffic control device or object struck contain information that can infer that the crash is a work zone crash. No work zone file or highway inventory is available. Level 1 Analysis The Level 1 analysis can be the most complete because data is available on the boundaries and duration of each work zone, the highway inventory can be searched for physical characteristics of the road where the work zone was located, and crashes identified as work zone crashes can be analyzed and compared to total accidents. This analysis also can be used to compute exposure num- bers for work zones and to compare crash rates for work zone and non-work zone conditions. The list below shows the types of analyses that can be completed for Level 1. Summarize the following types of crashes: • Crashes by road type • Crashes by type of work (construction, maintenance, and utility) • Crashes by crash type • Crashes by project type (paving, bridge work, night work, etc.) • Crashes by work zone type (lane closure, diversion, shoul- der work, etc.) Once these summaries are available, the following compar- isons should be made: • Work zone rates to non-work zone rates for road type and type of work. • Work zone rates to non-work zone rates for work zone type • All fatal crashes to work zone fatal crashes • Total crashes to work zone crashes • All fatal and injury crashes to work zone fatal and injury crashes In addition to these comparisons, the following analysis should be completed for a sample of the construction projects completed in the current year: • Number of crash reports coded as work zone crashes versus the number of crashes found by query using location and date • Determine the number of crashes that were related to work activity One type of analysis that is done by the Ohio DOT is shown in Exhibit X-1. This exhibit shows 15 long-term inter- state projects, the duration and length of each project, and an average AADT for the project. The projects were constructed during 2002. With this information, crash rate is determined for each proj- ect and an average crash rate is computed for all 15 projects (1.68 crashes/mvm as shown in Exhibit X-1). Fatality and fatal plus injury rates can also be computed. A free-flow comparable rate is also computed for 15 projects using crash data from 1999 to 2002. While details for each project are not available from Ex- hibit X-1, the free-flow projects should be comparable in road type and they could be the same roadway before construction. The AADTs listed would normally come from the highway inventory file, but the work zone AADTs should be determined from counts made during the work zone operations. At this level of analysis, crash rates for sections within a proj- ect can be computed by using the work zone file. Exhibit X-2 compiled by the Ohio DOT shows comparison of work zone sections versus pre-work zone 3-year averages for the same section. Note that 3-year averages were taken for the same months (4/15–11/15) in order to remove seasonal effects of crashes from any comparisons. The results of the Level 1 analysis should be detailed enough to point to crash reduction strategies. Road types 80

Exhibit X-1. Historical crash data analysis (Ohio DOT).

when work zone rates are 50 to 100 percent greater than pre- work zone rates should be examined on a project-by-project basis. In Ohio, analyses of work zone crashes revealed that many safety problems involved Interstate work zones with se- vere congestion levels. If work zones on high volume road- ways are a specific problem, then strategies aimed at reducing the number, duration and impact of work zones should be examined. Project level reviews of crash data revealed nu- merous crashes near on- and off-ramps. This result pointed to Strategy 19.1 C1 – establish work zone design guidance, and Strategy 19.1 A1 – improved maintenance and construc- tion practices. Specific details were added to Ohio’s contract documents to reduce these crashes. There was also greater use of night and weekend work schedules to minimize congestion in work zones as discussed in Strategies 19.1 A4 – use night- time work zones, and 19.1 F2 – improve coordination, planning, and scheduling of work activities. Level 2 Analysis In a Level 2 analysis, work zone crashes are flagged, and a highway inventory is available that can be linked to crash data. However, there is no file of work zone dates and locations. Without the work zone file, it is not possible to categorize work zone crashes by type of work, project type, or work zone type. Since it is not possible to determine work zone locations and dates, it is not possible to determine exposure or to com- pute work zone crash rates. An example of a Level 2 analysis conducted by a state highway agency is shown in Exhibit X-3. This exhibit shows the frequency of work zone crashes by severity level and road type. Severity of work zone crashes can be compared to the severity of all crashes. Also the severity of work zone crashes by road type can be compared to the severity of all crashes by road type. Other computations are possible in the Level 2 analyses in- cluding the type of crash for work zone crashes, the month, day of the week, and time of day that work zone crashes occur. The greatest weakness of this analysis is the lack of exposure information. This means that statistics, such as 85 percent of work zone crashes occur during daytime, are difficult to interpret without knowing what percent of work is being done during daytime, or the percent of vehicle miles of travel that take place in daytime work zones. It is also not possible to examine a portion of a work zone to find crash concentrations such as shown in Exhibit X-2. At any analysis level other than Level 1, the Strategy 19.1 F1-develop/enhance agency level work zone crash data systems should be considered. To enhance this Level 2 analysis, an agency would need to establish a work zone file that contains 82 Exhibit X-2. Application outputs (Ohio DOT).

83 07/03/08 IOWA WORK ZONE CRASHES (BY HIGHWAY SYSTEM AND CRASH SEVERITY) Year F I PDO F I PDO F I PDO F I PDO F I PDO 1978 0 5 16 2 47 71 0 11 15 0 35 51 2 98 153 253 1979 0 5 51 0 33 64 0 11 19 0 38 79 0 87 213 300 1980 1 9 20 1 19 49 1 11 19 0 38 79 3 77 167 247 1981 2 5 15 1 38 52 0 10 18 0 28 57 3 81 142 226 1982 1 7 19 1 36 40 0 14 15 0 19 30 2 76 104 182 1983 3 12 25 2 49 57 0 6 9 1 27 43 6 94 134 234 1984 2 36 56 3 67 88 2 7 14 0 27 42 7 137 200 344 1985 2 17 42 4 58 81 0 10 12 0 24 39 6 109 174 289 1986 0 32 76 0 42 64 1 12 16 0 32 51 1 118 207 326 1987 5 21 7 0 57 101 1 10 16 0 17 35 6 105 159 270 1988 2 44 100 2 44 71 1 11 19 1 22 63 6 121 253 380 1989 0 43 110 2 38 85 2 11 18 0 20 51 4 112 264 380 1990 2 29 89 1 61 90 0 8 14 1 31 51 4 129 244 377 1991 5 32 101 3 50 88 0 11 16 0 30 62 8 123 267 398 1992 3 43 79 3 48 63 1 12 14 1 23 48 8 126 204 338 1993 3 55 76 1 35 65 0 13 19 0 32 49 4 135 209 348 1994 10 58 77 1 76 63 1 12 8 0 23 55 12 169 203 384 1995 2 47 77 1 51 53 0 12 15 0 29 53 3 139 198 340 1996 1 34 47 1 71 82 1 14 14 0 30 66 3 149 209 361 1997 5 49 61 5 56 69 0 14 10 0 31 55 10 150 195 355 1998 4 30 39 4 61 64 1 12 17 0 18 34 9 121 154 284 1999 4 45 69 13 85 89 0 12 12 0 31 56 17 173 226 416 2000 1 40 44 5 68 62 0 12 19 0 31 45 6 151 170 327 2001 1 n/a n/a 7 n/a n/a 0 n/a n/a 0 n/a n/a 8 n/a n/a n/a 2002 3 n/a n/a 0 n/a n/a 0 n/a n/a 0 n/a n/a 3 n/a n/a n/a 2003 5 n/a n/a 0 n/a n/a 0 n/a n/a 0 n/a n/a 5 n/a n/a n/a 1991 to 2000 38 433 670 37 601 698 4 124 144 1 278 523 80 1436 2035 3551 Totals 1991 to 2000 3.8 43.3 67.0 3.7 60.1 69.8 0.4 12.4 14.4 0.1 27.8 52.3 8.0 143.6 203.5 355.1 Average Note: F = Fatality (Number of Actual Fatalities) Prepared By : Mark R. Bortle, PE I = Injury (Number of Injury Crashes) Office of Construction PDO = Property Damage Only (Number of PDO Crashes) Data From : Office of Traffic and Safety Highway Division Iowa Department of Transportation Interstates State Highways County Roads City Streets TOTAL CRASHES Crash Type Totals Exhibit X-3. Example of a statewide work zone crash summary.

the dates and locations of all work zones. This file could be started considering only long-term construction projects on Interstates and state highways. If results of this analysis show that most work zone fatalities are occurring on Interstates, then crash reduction strategies such as 19.1 A2-utilize full-time roadway closure for construc- tion operations, or 19.1 F4-implement work zone quality assurance procedures could be implemented. If work zone crashes are concentrated in the daytime or weekdays, Strategy 19.1 A4-use nighttime road work could be considered. Strategy 19.1 F2-improve coordination, planning and scheduling of work activities may also be effective in work zone crash reduction. If the percentage of pedestrian, bicyclists or motorcyclists crashes is larger than for total crashes, then Strategy 19.1 C3-improve work zone safety for pedestrians, bicyclists and motorcyclists should be considered. A large number of pedes- trian crashes may also indicate worker crashes that are traffic crashes, as opposed to worker occupational injuries. This pat- tern would point to Strategy 19.1 B4-reduce flagger exposure to traffic, or Strategy 19.1 C2-implement measures to reduce work space intrusions and limit consequences of intrusions. Level 3 Analysis In Level 3 analysis, work zone crashes are flagged but there is no work zone file or highway inventory. This analysis is de- pendent on crashes being flagged and how much information is obtained once they are flagged. If four fields are collected as recommended by the MMUCC then the Level 3 analysis can be expanded to consider the type of work zone, the location within the work zone, and if workers are present at the time of the crash. If the crash is simply flagged as a work zone crash with no further details, the Level 3 analysis will be limited to a determination of the frequency and severity of work zone crashes versus all crashes in an agency. Exhibit X-4 is taken from A Guide for Reducing Work Zone Collisions (17). While this exhibit contains only fatal crash data, it is representative of the types of comparisons that can be made in the Level 3 analysis. Results are typical of work zone crash characteristics. Results from this exhibit are outlined in A Guide for Reducing Work Zone Collisions and are typical of fatal work zone accidents: • Almost 30 percent of fatal work zone crashes occurred on urban or rural interstates, and this is more than double the percentage of all fatal crashes. • Rear-end fatal crashes were over 2.5 times more common in work zones than in all fatal crashes. • Work zone fatal crashes are more common in the summer months than all fatal crashes. • Almost 60 percent of work zone fatal crashes occurred on roads with posted speed limits of 55 mph or greater. • Work zone fatal crashes are more likely to involve more than 2 vehicles than all fatal crashes. This analysis is limited by the available data and many of the results from Exhibit X-4 could be related to exposure. In other words, more work zones occur in summer months and therefore the proportion of work zone crashes is higher in summer months than all crashes. At this level, Strategy 19.1 F1-develop/enhance agency level work zone crash data systems should be considered. The ad- dition of a highway inventory that is linked to crash data and a work zone file that gives dates and locations of work zones would enable a much more comprehensive analysis. If rear-end and multiple-vehicle crashes are more pre- dominant in work zones than for all crashes, Strategy 19.1 B2-improve visibility of work zone traffic control devices and Strategy 19.1 D2-improve credibility of signs should be im- plemented. If work zone crashes are concentrated in the daytime or weekdays, then Strategy 19.1 A4-use nighttime road work and Strategy 19.1 F2-improve coordination, planning and scheduling of work activities may be effective in work zone crash reduction. A large proportion of single vehicle crashes in work zones may be a trigger to consider Strategy 19.1 B2-improve visi- bility of work zone traffic control devices (particularity bar- riers), Strategy 19.1 B3-improve visibility of work zone per- sonnel and vehicles, and Strategy 19.1 C2-implement measures to reduce work space intrusions (and limit conse- quences of intrusions). Level 4 Analysis If there is no flag for indicating a work zone crash, then it may be impossible to determine the nature of work zone crashes or if they are even a problem that should receive a pri- ority treatment. Some crash forms do include fields that might indicate crashes related to work zones such as an item for “barricade” under traffic control, or “under repair” item in the road condition field. It may also be possible to manu- ally request the reports for recent major projects, and exam- ine these crashes to determine the nature of the work zone crash problem. Strategy 19.1 F1-develop/enhance agency level work zone crash data systems should be a priority if no flag is available on the crash data form to indicate a work zone crash. 84

85 Factor All Fatal Crashes (Percent) Work Zone Fatal Crashes (Percent) Time of Day Night 49 47 Day 50 52 Unknown 1 1 Day of Week Weekend 34 31 Weekday 66 69 Season Winter 22 16 Spring 24 26 Summer 27 31 Autumn 27 27 Roadway Function Rural, Interstate 7 13 Rural, Other 51 39 Urban, Interstate 6 15 Urban, Other 35 32 Unknown 1 1 Speed Limit 1–50 mph 44 38 55–75 mph 52 58 Unknown 4 4 Number of Vehicles Involved One 57 53 Two 36 35 More Than Two 7 12 Manner of Two-vehicle Collision Rear-end 13 35 Head-on 26 21 Angle 32 22 Side-swipe, Opposite Direction 21 15 Side-swipe, Same Direction 6 7 Other or Unknown 2 1 Exhibit X-4. Comparison of factors: percentages of work zone and non-work zone fatal crashes (data from FARS, 2003).

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TRB's National Cooperative Highway Research Program (NCHRP) Report 500, Vol. 21: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan: Safety Data and Analysis in Developing Emphasis Area Plans provides guidance on data sources and analysis techniques that may be employed to assist agencies in allocating safety funds.

In 1998, the American Association of State Highway and Transportation Officials (AASHTO) approved its Strategic Highway Safety Plan, which was developed by the AASHTO Standing Committee for Highway Traffic Safety with the assistance of the Federal Highway Administration, the National Highway Traffic Safety Administration, and the Transportation Research Board Committee on Transportation Safety Management. The plan includes strategies in 22 key emphasis areas that affect highway safety. The plan's goal is to reduce the annual number of highway deaths by 5,000 to 7,000. Each of the 22 emphasis areas includes strategies and an outline of what is needed to implement each strategy.

Over the next few years the National Cooperative Highway Research Program (NCHRP) will be developing a series of guides, several of which are already available, to assist state and local agencies in reducing injuries and fatalities in targeted areas. The guides correspond to the emphasis areas outlined in the AASHTO Strategic Highway Safety Plan. Each guide includes a brief introduction, a general description of the problem, the strategies/countermeasures to address the problem, and a model implementation process.

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