The HAL Manual is a term used for the “Manual on Identification, Analysis and Correction of High-Crash-Locations” (Third Edition - 1999). The First Edition of the HAL Manual was published in 1975. The HAL Manual allowed local, non-MoDOT agencies to
- Develop a traffic record system (Chap 2)
- Identify high crash locations (Chap 3)
- Analyze high crash locations (Chap 4)
- Correct high crash locations (Chap 5) and
- Evaluate the benefits of correcting high crash locations (Chap 6).
While the HAL Manual was intended for local agencies and law enforcement, it has become a tool for MoDOT personnel as well. The HAL Manual is not MoDOT policy, but only a supplemental document to the Engineering Policy Guide (EPG). Any information in the HAL Manual that relates to topics in the EPG, the EPG takes precedence.
|MoDOT’s safety engineers constantly search for the best practices in the field to improve Missouri roadways’ safety.|
MoDOT has developed a traffic record system focused on the state maintained roadways and is developing the non-state maintained system. MoDOT’s traffic record system is also called the Transportation Management System (TMS). The TMS system uses roadway and crash information to develop High Severity lists for intersections and ranges. Districts are responsible to review these lists to develop their safety program strategies.
While identifying high crash corridors, Chapter 3 of the HAL Manual explains some of the types of crash rates used when comparing locations. When comparing locations for a safety analysis, crashes are typically normalized by rate. Some of the rates covered by the HAL Manual that are used in MoDOT studies include:
- Number of crashes
- Crash severity (EPDO – Equivalent Property Damage Only)
- Crash rate
- Severity Rate (EPDO by rate)
- Number-Quality-Control & Rate-Quality-Control
After high crash locations are identified, Chapter 4 of the HAL Manual recommends information to gather to complete a traffic study. The procedure outlined in the HAL Manual can be applied to any request for a field study. The first recommendation is to review crashes and complete a collision diagram. A collision diagram (HAL Manual, Figure 4-1) is a spot map that shows where crashes are occurring, either within the intersection or along the range. The collision diagram will show the vehicle action, angle of collision and general location of the crash compared to the roadway. Other information important to the crash is included such as date, time of day, roadway/weather conditions, crash severity, etc. The TMS Accident Browser application uses computer software to produce an automated collision diagram for a single intersection. The collision diagram aids in identifying the predominant crash pattern at that location.
Another process in a traffic study is to perform an on-site observation. Depending on the crash history, it may be important to perform the observation both during the day and at night. The location should be driven from each direction. If there is a possibility for pedestrian travel, the location should be walked in order to view the road, as a pedestrian would experience it. The on-site report (HAL Manual, Figure 4-2) should identify the location of the observation points, identify potential hazards by making a physical checklist, make notations regarding pedestrian and driver activity, take photos and interview local people for their observations of the location. When identifying potential hazards, it is important to draw a condition diagram (HAL Manual, Figure 4-3), a drawing (to scale, if practical), of the existing roadway, control device locations and major features in the nearby environment. The condition diagram may also include physical road conditions, signing, striping, etc. that may be important in determining a countermeasure analysis. Also included when performing a field observation are traffic counts, spot speed studies and sight distance evaluations. The HAL Manual has included worksheets to assist in the development of the location analysis (HAL Manual, Figure 4-4).
According to Chapter 5 of the HAL Manual, after the locations have been identified, crashes analyzed and field data gathered, the corrective actions are determined. With most locations, there are potential low cost solutions, medium cost solutions, and high cost solutions. Appendix B in the HAL Manual helps determine probable causes for crash patterns and general countermeasures. Since the HAL Manual was last produced in 1999, the NCHRP 500 series has been studied and published to help determine probable cause and select countermeasures. The NCHRP 500 series is more up-to-date with current engineering practices than the existing HAL Manual.
When the potential countermeasures are identified, they need to be compared through a benefit/cost (B/C) analysis. A B/C analysis compares the estimated cost of the countermeasure compared to the benefit expected through crashes reduced. Figure 5-1 of the HAL Manual has spreadsheets available to assist in calculating a B/C analysis . The most practical countermeasure may not have the most favorable benefit/cost ratio. To help calculate a B/C, Appendix G is used to estimate crash reduction factors for most improvement types. There is currently a national effort to develop a Highway Safety Manual that will include the most current estimated crash reduction factors.
When using Safety Funds, a project evaluation is needed to determine whether the selected countermeasures are effective. To do this, a before/after (B/A) safety analysis should be performed. For a B/A study, the crash history of a location is reviewed for a 3- to 5-year period before and after the installation/construction of the countermeasure (HAL Manual, Figure 5-2). An evaluation can also be calculated to determine the actual B/C ratio based on actual costs and crashes reduced (HAL Manual, Figure 6-1).