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

Chapter: Section IX - Special Vehicles

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Suggested Citation:"Section IX - Special Vehicles." 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 IX - Special Vehicles." 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 IX - Special Vehicles." 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 IX - Special Vehicles." 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 IX - Special Vehicles." 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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74 Planning Programs Aimed at Reducing Crashes Involving Large Trucks and Motorcycles This section of the guide provides the details of choosing treatment strategies for reducing crashes involving special ve- hicle types, such as large trucks and motorcycles. As indicated earlier, it is assumed at this point that the analyst has chosen his or her emphasis area or areas (e.g., large trucks or motor- cycles) and has established a stretch goal for crash reduction. Four procedures for choosing and targeting treatment strate- gies were described in the Stage 3 text in Section III. Three of those procedures require that the effectiveness of at least some of the potential treatment strategies be known – that the treatments have a known CRF or AMF. However, almost none of the strategies in the guides related to these special ve- hicle types have known effectiveness. For that reason, only the details of Procedure 3 will be covered in this section. If AMFs are developed for treatments for these populations, or if the analyst is only interested in examining the few treatments with known AMFs, then the economic-based Procedures 1 or 2 can be used. If AMFs exist for some of the treatments of po- tential interest but not for all (which will likely be the case in the near future), Procedure 4 can be used. While the crash types will differ, details of the use of all three of these “known- effectiveness procedures” are provided in Section IV on “Roadway Segment Programs.” Thus, the basic steps in Procedure 3 presented below will be appropriate for all four of the special vehicle types covered in this section. The data will differ, but the basic procedure will re- main the same. The analyst is strongly urged to carefully review the material in each of the pertinent guides before beginning this planning process. These user-population-oriented guides are found within the NCHRP Report 500 guide series. The specific volumes pertinent to this section are: • Volume 13: A Guide for Reducing Collisions Involving Heavy Trucks (13) • Volume 22: A Guide for Reducing Collisions Involving Mo- torcycles (pending) A link to these downloadable guides can be found at http:// safety.transportation.org/guides.aspx. Procedure 3 – Choosing Treatments and Target Subgroups for Crashes Involving Special Vehicle Types When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Not Known Again, the assumption here is that there is no known level of effectiveness for the treatment strategies of interest – no defined CRFs or AMFs. Thus, economic analyses like those that are the basis for Procedures 1, 2A, 2B, and 4 are not pos- sible for these treatments. This Procedure 3 is aimed at help- ing the analyst make an educated choice of which treatments will be most effective in his or her jurisdiction, and to help the analyst develop a targeting strategy for the treatment in cases where it is not to be applied jurisdiction-wide (e.g., where specific vehicle subpopulations or roadway locations are to be targeted). In general, within each user group, the choice between alternative treatments will be based on the specific nature of the population’s crash problem, and the choice of target subgroups will be based on the determination of where the crash/injury problem of interest is found. A discussion of this more general procedure was included under the Proce- dure 3 subheading in Section III, and the reader should review that section. Data Needs The only required data for Procedure 3 are crash data that will allow the analyst to (1) isolate crashes involving the spe- cific vehicle types of interest (e.g., large trucks or motorcy- cles), and (2) define crash types for these vehicle types that would suggest strategies and target subgroups. S E C T I O N I X Special Vehicles

75 To isolate crashes involving the vehicle types of interest, the analyst will need to examine the data formats/coding in his or her crash file to identify variables that can be used in determin- ing whether or not a given crash is a “target-population crash.” Crash databases often categorize data for a given crash into up to three subfiles – (1) general accident/crash variables (“crash”), (2) variables for each vehicle in the crash (“vehicle”), and (3) variables for each occupant/person in the crash (“person” or “occupant”). The variable needed to determine whether a crash involves a specific vehicle type is, by definition, found in the ve- hicle subfile. Trucks and motorcycles are nearly universally among the vehicle types identified explicitly in the vehicle sub- file data. There are state-to-state variations in the number and nature of truck type categories that are explicitly identified in crash data. Motorcycles are virtually never categorized into sep- arate motorcycle types in crash data. Example variables used to identify these two vehicle types are shown in Exhibit IX-1 below. Defining crashes that will guide the choice of treatment strat- egy and the targeting of these strategies will require crash data that includes specific variables and codes on such items as location of crash (intersection vs. non-intersection, ramp vs. mainline); condition of driver (e.g., impaired, fatigued); driver action prior to crash; driver license status (e.g., motorcycle license or endorsement); condition of vehicle, etc. Again, the names of variables and the specific codes needed to conduct these analyses will vary from jurisdiction to jurisdiction. Ex- hibit IX-2 provides some guidance concerning where example variables related to some treatment strategies might be found. Procedure As described in Section III, Procedure 3 has two basic steps. First, choose the “best treatments” for the user population of interest (e.g., the large truck or motorcycle treatments most likely to be applicable in a given jurisdiction) from among the set of all treatments presented in the applicable NCHRP Report 500 guides. Second, choose the subgroups of highway locations to which the selected treatments should be applied. As described earlier in more detail, the choice of the “best treat- ments” from the listing of many potential user-population treatments can be based on the following factors: a) The many potential treatments judged to be the most ef- fective, even given that effectiveness is unknown b) The relative magnitude of the crash types and severity levels that the treatment will affect c) The cost of the potential treatments (either jurisdiction- wide or per-mile or per-location) d) Other technical or policy considerations These factors must be combined in some fashion to decide which treatment to choose. While there are multiple ways of making this choice, the following represents one such procedure. 1. Prioritize the specific user-population problem(s) to be addressed. Here, the initial issue is whether to treat large truck crashes, motorcycle crashes or both. This prioritization will be based on the frequency and severity of the specific types of crashes by vehicle type occurring in an analyst’s jurisdic- tion. For each vehicle type, the analyst could begin the process by analyzing 3 to 5 years of crash data to determine the frequency of each population. However, since some crashes for specific vehicle types may vary in severity, total crash frequency alone does not provide the complete an- swer. While an alternative is to restrict the analysis to only fatal and serious-injury crashes, this will severely limit the crash sample, and will also omit a large component of the crash problem – non-serious injury and no-injury crashes. A better solution is to weight each crash for a given user population by an economic cost based on its severity, and then accumulate the total crash cost for each population. In the preceding sections of this guide, information on eco- nomic cost per crash severity level was extracted from Crash Cost Estimates by Maximum Police-Reported Injury Severity Within Selected Crash Geometries (22). Exhibit IX-3 presents those costs per crash. Costs for combinations of crash sever- ity levels (e.g., K+A crashes) are presented in that report (22). This analysis of total crash costs per year will provide the analyst with overall information on which vehicle types are most important in his/her jurisdiction. Note that the total crash cost calculated using these severity-based figures may not be as accurate for motorcycle Population Type Variable Crash Database Subfile Drivers of Heavy Trucks Vehicle Type Motor Vehicle Body Type Category Commercial Motor Vehicle Configuration Commercial Cargo Body Type Vehicle Vehicle Vehicle Vehicle Motorcycle Operators Vehicle Type Motor Vehicle Body Type Category Vehicle Vehicle Exhibit IX-1. Crash variables and subfile location by population type.

76 Crash Type/Issue Variable Crash Database Subfile Intersection vs. Non- intersection; Ramp-related Relation to Junction Type of Intersection Traffic Control Device Type Crash Crash Crash or Vehicle Lane Departure (Potentially Related To Pavement Markings) Accident/Crash Type Manner of Collision Sequence of Events First Harmful Event Most Harmful Event Crash Location (Off-road) Crash Crash Vehicle Crash Vehicle Crash Vehicle Equipment Problems Vehicle Defect Contributing Circumstances, Motor Vehicle Vehicle Vehicle Fatigue-related Crashes Fatigue Involvement Captured under “Driver Condition” (If Available) Person/Vehicle Alcohol-involved Crashes Alcohol Involvement Law Enforcement Suspect Alcohol Use Alcohol Test Violation Codes Crash Person/Vehicle Person/Vehicle Person/Vehicle Speed-related Crashes Driver Action Prior to Crash Violation Indicated Contributing Circumstances Person (or Vehicle) Person (or Vehicle) Person (or Vehicle) Work Zone Crashes Work Zone Related Roadway Condition Crash Crash Driver Age Driver Age Occupant Age Seating Position Person (or Vehicle) Person Person Motorcycle Helmet Use Occupant Protection System Used Person (or Vehicle for Driver) Driver License Status/ Motorcycle Endorsement Driver License Class Driver License Status Violation Codes Person (or Vehicle) Person (or Vehicle) Crash or Vehicle Driver Clothing Driver Protective Equipment (maybe) Person or Vehicle Crash Location (for Targeting Treatments) County City Route Milepost Longitude/Latitude Block Address Crash Crash Crash Crash Crash Crash Speed Limit (for Use in Developing Cost per Crash) Speed Limit Crash Exhibit IX-2. Crash variables and subfile location by crash type/issue. Crash Severity Speed Limit Category Comprehensive Cost/Crash* < 45 mph $3,622,200 Fatal (K) > 50 mph $4,107,600 < 45 mph $195,700 Serious Injury (A) > 50 mph $222,300 < 45 mph $62,200 Moderate Injury (B) > 50 mph $91,600 < 45 mph $40,100 Minor Injury (C) > 50 mph $49,500 < 45 mph $7,000 No Injury (O) > 50 mph $7,800 * Crash Cost in 2001 dollars (22) Exhibit IX-3. Crash cost by crash severity and posted speed limit.

and truck crashes as for crashes covered in other sections. The costs per crash in Council, et al. (22) were based on the full distribution of crashes and vehicles in crashes, and thus are predominately weighted by passenger vehicles. They are not based exclusively on truck or motorcycle crashes. Thus, they are based to some extent on the expected num- ber of occupants in all crash-involved vehicles who might be injured or killed in a crash of a given severity. Since heavy truck and motorcycle crashes involve a different mix of “occupants” than passenger cars, these figures may not be totally accurate. In the absence of other crash-cost fig- ures, it is suggested that these be used for motorcycle crashes. They could also be used for truck crashes for con- sistency with other vehicle types. However, a second study by Zaloshnja and Miller (28) presented costs specific to truck-involved crashes. Exhibit IX-4 presents cost- per-crash by crash-severity level for “all large trucks” from that report. The Zaloshnja and Miller report (28) does not categorize the cost by crash types or speed limits, but does categorize them by different large truck types (e.g., straight trucks, bobtail, truck-tractor with one trailer). Note also that crash costs shown here are converted from Year 2000 costs in Zaloshnja and Miller to Year 2001 costs to be consistent with other costs in this guide. The conversion was based on changes in the Consumer Price Index and followed procedures recommended in that report. 2. Prioritize the specific subpopulations to be addressed. Once one or more populations are identified, the second step involves the identification of subgroups in most need of treatment. Most of the strategies in the heavy truck guide are applicable to all truck crashes. Thus all crashes involving heavy trucks are treatable with these strategies. However, there are three truck strategies that appear to be more appli- cable to only selected crash types. The strategy related to truck rollover on interchange ramps is focused on this type of crash at this type of location. Strategies related to truck mechanical failure might be targeted to crashes involving truck defects, and the parking-related strategies might be considered applicable to fatigue-related truck crashes. Many of the strategies in the motorcycle guide are also applicable to all motorcycle crashes. In the cases of the road- way-related strategies presented there, it is difficult to define specific crash types that might be analyzed since many of these are suggestions for changing roadway design and maintenance problems (e.g., minimize roadway irregulari- ties such as potholes and lower manhole covers, reduce roadway debris, reduce or eliminate use of low traction materials in roadway markings). It does not appear that examining only crashes related to poor road condition would capture all applicable motorcycle crashes. However, one could examine motorcycle crashes occurring in work zones to determine the possible problem size for the strate- gies related to those zones. It would also be possible to identify alcohol-related motorcycle crashes and crashes involving motorcycle operators who are either unlicensed or not licensed to operate a motorcycle. With respect to strategies related to protective equipment, it will be difficult to identify crashes where more protective or more reflective clothing might be needed, but will be much easier to identify crashes in which the motorcycle operator was not wearing a protective helmet. In order to analyze the possible benefit of those truck or motorcycle strategies targeted to specific crash types or user subpopulations, crashes involving only the applicable subpopulations can be identified using variables in the table above (e.g., motorcycle operators not licensed to operate a motorcycle) and can be analyzed. Here, just as in Step 1, the prioritization of subpopulations can be based on the frequency and severity of the specific types of user-subpopulation crashes occurring in an analyst’s jurisdiction. For each user subpopulation or crash type, the analyst could analyze 3 to 5 years of crash data to determine the frequency of each crash population. Again, either total crashes or some subset (e.g., fatal and serious- injury crashes) could be used, but the economic cost of crashes is a better measure since crash severity may differ. The cost figures presented above could be used. 3. Identify possible treatments for use for each high-priority crash type. The analyst will then review the pertinent NCHRP Re- port 500 guides and list treatments that would be most ap- propriate for each of the high-priority crash types identi- fied in the above step. The choice should be limited to those treatment strategies that are classified as proven or tried in the guides. 4. Rate the possible treatments based on “estimated effectiveness.” Since this procedure deals with treatment strategies with unknown effectiveness, this appears to be impossible. However, for a given set of possible treatments for a par- ticular vehicle type, it may be possible to make a judgment concerning which treatment strategy would be expected to be most effective. For example, strategies related to chang- ing the roadway may be more effective, in general, than strategies related to education (but, of course, will affect only those users at the treated locations). At times, this will clearly be a very difficult judgment to make. 77 Crash Severity Comprehensive Cost/Truck Crash* Fatal (K) $3,370,648 Serious Injury (A) $138,841 Moderate Injury (B) $62,779 Minor Injury (C) $52,412 No Injury (O) $10,713 * Converted to 2001 dollars (28) Exhibit IX-4. Truck crash cost by crash severity.

78 5. Choose best treatment(s) by considering estimated effectiveness, cost and other technical and policy considerations. The analyst will then combine the output of the steps above with at least two other factors in making a final decision on which treatment(s) to implement – the cost of the treatment and other technical and policy considera- tions. Unfortunately, there are no good guidelines for how to “weight” the different factors. While problem size (total crash cost) and assumed treatment effectiveness are key factors, there may be technical, policy, and cost consider- ations that will remove certain treatments from consider- ation even if they are felt to be effective. The analyst will have to choose the final treatments based on best judg- ment. The procedure outlined above will at least ensure that the major factors in the decision are clearly defined. The output of this step will be one or more chosen treat- ments, with the nature of the treatment defining the spe- cific crash types more likely to be affected. 6. Target the chosen treatments to the vehicle types and crash types where the problem is found. In some cases, treatment strategies related to these vehicle types will be implemented jurisdiction-wide. In other cases, it may be desirable to target the treatment to specific loca- tions. If targeting is to be done by location, the treatment could be targeted to counties, city areas, or routes/streets showing the highest total crash cost or frequency, coupled with the analyst’s judgment of potential differences in cost between locations and technical and political issues. Most of the strategies in these two guides are related to treating the driver or vehicle, rather than the roadway, and this targeting to jurisdiction would appear to be the most appropriate. It would be difficult to target further by crash type or other fac- tors. If the analyst is considering the roadway-related strate- gies, and if the crash data are mileposted, the analyst could (1) link crashes to routes and search for the locations of “clusters” of target crashes for possible treatment, or (2) use a network screening program similar to that described under Procedure 2A to identify 1-mile sections with the highest crash frequency or total crash cost. The identified windows could then be ranked by frequency or total crash cost to identify priority locations. The analyst would then correct for “treatment gaps” using the same logic provided in Pro- cedure 2A (see Section IV). If the crashes are not mileposted, but there is information available on jurisdiction and route, the analyst could link crashes to routes within the jurisdic- tion and calculate the total crash cost or number of target crashes per mile by dividing the sum of the crash costs or the sum of the number of target crashes on that route by route length. The analyst could then rank the potential routes for treatment based on this rate per mile, and choose the routes to be treated based on the highest rankings plus other tech- nical and policy factors. An excellent example of location-specific targeting that can be done if crashes are mileposted to specific roadway locations involves ramp treatments to prevent or reduce truck rollovers. If ramp-related crashes (based on “rela- tion to junction”) are mileposted, even if just to the inter- change mainline, the analyst can determine which specific interchanges and ramps exhibit the largest problem. Note again that the lack of treatment effectiveness data means that the analyst will not be able to verify whether or not a specific set of implemented strategies can be expected to meet the established crash-reduction goal. In these cases, the best that can be done is to proceed in selecting strategies and target subgroups, times or locations until the available budget for safety improvement has been fully committed. The total benefit of the selected program will not be forecastable, but the success of the program can be determined if a sound evaluation is conducted after its implementation. Where quantitative estimates or approximations of treat- ment effectiveness can be made, it may be possible to pro- vide estimates of net impact (number of crashes prevented) by multiplying the unit treatment effects by the number of drivers or roadway segments treated. Closure – Good Data Produce Better Results Choosing treatments and targeting those treatments to the vehicle populations covered in this section is difficult. The programs are complex, there is virtually no crash-based information on treatment effectiveness for the strategies cov- ered in the two guides, and there is limited information on program costs. However, choices have to be made given that available budgets will always be limited to some degree. It is hoped that the procedures presented in this section at least provide some insight into how such choices can be made. The assumption in this section has been that crash data are available, but not necessarily other data such as roadway in- ventories. As is obvious in the procedures above, the avail- ability of mileposted crash data will result in improved treat- ment targeting for roadway-related strategies (and perhaps enforcement strategies), and the availability of linkable (and thus mileposted) inventory data would further increase the analyst’s ability to both choose treatment strategies and to target them. For example, inventory data could provide detailed data not found in crash data files on such items as sig- nal timing, intersection layout, and street width, all of which are related to treatment strategies listed in the guides.

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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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