Skip to main content

Currently Skimming:


Pages 10-55

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 10...
... SECTION V Description of Strategies Objectives of the Emphasis Area The objectives for reducing the number of head-on fatal crashes are: • Keep vehicles from departing the traveled way • Minimize the likelihood of head-on crashes with an oncoming vehicle • Reduce the severity of median barrier crashes that occur • Enhance enforcement and awareness of traffic regulations • Improve coordination of agency safety initiatives These objectives are similar to those cited for run-off-road crashes (emphasis area 15.1, Volume 6 of this guide) and head-on collisions (emphasis area 18.1, Volume 4 of this guide)
From page 11...
... Types of Strategies The strategies in this guide were adopted from a number of sources, including recent literature, contact with state and local agencies throughout the United States, and federal programs. Some of the strategies are widely used, while others are used at a state or local level in limited areas.
From page 12...
... SECTION V -- DESCRIPTION OF STRATEGIES Related Strategies for Creating a Truly Comprehensive Approach The strategies listed above, and described below in detail, are those considered unique to this emphasis area. However, to create a truly comprehensive approach to highway safety issues and problems associated with this emphasis area, there are related strategies recommended as candidates for possible inclusion in any program-planning process related to addressing head-on crashes for freeways.
From page 13...
... • Enforcement of Traffic Safety Laws -- Well-designed, well-operated law enforcement programs can have a significant effect on highway safety and must be an element in a strategic and comprehensive highway safety program. It is well established, for example, that an effective way to reduce crashes (and their severity)
From page 14...
... SECTION V -- DESCRIPTION OF STRATEGIES Strategy 18.2 A1 -- Install Left Shoulder Rumble Strips (T) The purpose of rumble strips is to alert drivers who may inadvertently stray or encroach into the median.
From page 15...
... SECTION V -- DESCRIPTION OF STRATEGIES V-6 EXHIBIT V-2 (Continued) Strategy Attributes for Left Shoulder Rumble Strips (T)
From page 16...
... SECTION V -- DESCRIPTION OF STRATEGIES V-7 EXHIBIT V-2 (Continued) Strategy Attributes for Left Shoulder Rumble Strips (T)
From page 17...
... Strategy 18.2 A2 -- Provide Enhanced Pavement Markings and Median Delineation (T) General Description The main focus of this strategy is to provide better pavement marking guidance and delineation where there is a possibility for a driver leaving the roadway.
From page 18...
... SECTION V -- DESCRIPTION OF STRATEGIES Raised pavement markers provide delineation over a wider range of environmental conditions than can be achieved with standard pavement marking materials. There are a variety of types and models in the form of snow plowable and non-snow plowable markers.
From page 19...
... SECTION V -- DESCRIPTION OF STRATEGIES V-10 EXHIBIT V-4 (Continued) Strategy Attributes for Enhanced Pavement Markings and Delineators (T)
From page 20...
... SECTION V -- DESCRIPTION OF STRATEGIES V-11 EXHIBIT V-4 (Continued) Strategy Attributes for Enhanced Pavement Markings and Delineators (T)
From page 21...
... Strategy 18.2 A3 -- Provide Improved Pavement Surfaces (T) FARS statistics from 2001 show that 13 percent of cross-median crashes on Interstates occur on wet surfaces and 4 percent occur on roadways with snow and ice.
From page 22...
... SECTION V -- DESCRIPTION OF STRATEGIES V-13 EXHIBIT V-5 Strategy Attributes to Provide Improved Pavement Surfaces (T) Attribute Description Technical Attributes Target Expected Effectiveness Keys to Success Potential Difficulties Appropriate Measures and Data Associated Needs Organizational and Institutional Attributes Organizational, Institutional and Policy Issues Treatment will target locations where skidding or poor pavement surface is determined to be a problem, in wet or dry conditions.
From page 23...
... Objective 18.2 B -- Minimize the Likelihood of Head-on Crashes with an Oncoming Vehicle This objective considers the situation in which the vehicle has already left the lane and is in the median. The strategies involve preventing the vehicle from crossing over into the other direction of travel and being involved in a cross-median head-on crash, and helping to redirect the vehicle in the direction of flow.
From page 24...
... SECTION V -- DESCRIPTION OF STRATEGIES which includes the inside shoulders. Often right-of-way restrictions dictate the availability of median width.
From page 25...
... SECTION V -- DESCRIPTION OF STRATEGIES V-16 EXHIBIT V-6 Strategy Attributes for Use of a Wider Median (P) Attribute Description Technical Attributes Target Expected Effectiveness Keys to Success Potential Difficulties Appropriate Measures and Data Associated Needs Organizational and Institutional Attributes Organizational, Institutional and Policy Issues Provide more recovery area for the errant vehicle in the form of a wider median for the vehicle which crossed the lane unintentionally.
From page 26...
... SECTION V -- DESCRIPTION OF STRATEGIES V-17 EXHIBIT V-6 (Continued) Strategy Attributes for Use of a Wider Median (P)
From page 27...
... roadway edge is at a 90° angle to the shoulder surface. Near-vertical edge drop-offs of less than 4 inches are still considered a safety hazard to the driving public and may cause difficulty upon reentry to the paved surface.
From page 28...
... SECTION V -- DESCRIPTION OF STRATEGIES Improve Median Slope Design Related to Head-on Crashes There appear to be trade-offs when considering the design of a median and its effect on mitigating various crashes. Assuming a vehicle has left the traveled way, the objective of a median design should be two-fold: one, to provide a safe recovery area for the errant vehicle without rolling over, and two, to not have the errant vehicle cross the median and crash head-on with oncoming cars.
From page 29...
... Flattening the slopes of narrow medians should be approached with care. Although it will increase the likelihood of safe recovery, flattened slopes may allow an errant vehicle to more easily cross the median into opposing traffic.
From page 30...
... SECTION V -- DESCRIPTION OF STRATEGIES Strategy 18.2 B3 -- Install Median Barriers for Narrow-Width Medians (P) This strategy involves providing a barrier to separate opposing traffic on a divided highway.
From page 31...
... 60,000 vehicles per day would be candidates for a median barrier study. Caltrans also uses an accident study warrant to identify sections of freeway that may require median barriers.
From page 32...
... SECTION V -- DESCRIPTION OF STRATEGIES ditch. Based on computer simulation and limited crash testing, current guidance is that placement of cable barriers should be avoided in the area from 0.3 m (1 ft)
From page 33...
... The proposed revisions to AASHTO's Roadside Design Guide include reference to several High-Tension Cable Barrier systems that have been developed and are increasing in use. Please refer to the Roadside Design Guide for additional details on the various barriers and to the appendixes of NCHRP Report 500, Vol.
From page 34...
... SECTION V -- DESCRIPTION OF STRATEGIES The FARS database for the year 2003 showed that 19 percent of the head-on crashes which occurred on Interstates and expressways were on a divided highway median with a traffic barrier installed. From these data it is unlikely to say that barriers can eliminate crossover median head-on crashes.
From page 35...
... Not only the installation of the median barrier, but also the maintenance of the median barrier is relatively important, since median barriers such as the three-cable barrier, in some cases, become less effective after every collision. In some cases, periodic re-tensioning of the cables is necessary for its effective performance.
From page 36...
... SECTION V -- DESCRIPTION OF STRATEGIES V-27 South Carolina DOT (SCDOT) installed 315.5 miles of three-strand cable on Interstate segments with median widths less than 60 ft wide.
From page 37...
... SECTION V -- DESCRIPTION OF STRATEGIES V-28 Keys to Success Ignoring the I-5 Marysville crashes, the study found that collisions with cable barrier were significantly less likely to involve multiple vehicles than guardrail and concrete barriers. Also, less than half as many injuries and fatalities occur when a single vehicle collides with cable barrier compared to guardrail or concrete barrier.
From page 38...
... SECTION V -- DESCRIPTION OF STRATEGIES V-29 Potential Difficulties Appropriate Measures and Data light vans and trucks adequately. Research in Florida, for example, indicated that in only two percent of the "across-median" crashes investigated was the crossing vehicle larger than a passenger car.
From page 39...
... SECTION V -- DESCRIPTION OF STRATEGIES V-30 Associated Needs Organizational and Institutional Attributes Organizational, Institutional and Policy Issues Issues Affecting Implementation Time Costs Involved As the drivers are familiar with the barriers, there doesn't appear to be a need for any public information and education initiative. These strategies will be implemented by state and local roadway agencies, and it doesn't appear that extra coordination with other agencies or groups is needed.
From page 40...
... SECTION V -- DESCRIPTION OF STRATEGIES V-31 Training and Other Personnel Needs Legislative Needs Other Key Attributes Compatibility of Different Strategies Other Key Attributes to a Particular Strategy The repair costs of cable barrier for four states are compared below: Accident Cost Comparisons North New Oregon, Carolina, Iowa, York, 1998 1995 1978 1969 Km Cable Median Barrier 14.5 13.7 NA NA Police- and State-Reported Accidents/Year 20 NA 16 125 Repairs/Year 40 71 29 NA Number of Fatalities/Year 0 0 0.5 1.3 Number of Injury Accidents/Year 3.8 21.1 2.5 6.0 Repair Cost/Accident (Study Year) $735 NA $212 $90 Repair Cost/Accident (1998 $)
From page 41...
... SECTION V -- DESCRIPTION OF STRATEGIES V-32 relatively infrequent, they are more likely to produce serious injuries and fatalities compared to other types of freeway crashes. Statistics from the Fatality Accident Report System (FARS)
From page 42...
... SECTION V -- DESCRIPTION OF STRATEGIES V-33 Strategies that are directed at preventing wrong-way movements range from relatively inexpensive, such as signing and pavement marking, to very costly, such as intelligent transportation system (ITS) applications.
From page 43...
... visible to the driver from the decision point on each likely wrong-way approach. California, Georgia, and Virginia are three states that have adopted this signing approach.
From page 44...
... SECTION V -- DESCRIPTION OF STRATEGIES Additional traffic control measures used by some states, and worthy of consideration, include the use of low mounted "One Way" arrow signs, the addition of a 24-in. wide painted stop bar at the crossroad end of the ramp, and supplementary "Ramp" and "Freeway" signs.
From page 45...
... SECTION V -- DESCRIPTION OF STRATEGIES V-36 Keys to Success Potential Difficulties Appropriate Measures and Data Associated Needs Organizational and Institutional Attributes Organizational, Institutional and Policy Issues Issues Affecting Implementation Time Ohio DOT in the Columbus area experienced 17 wrong-way crashes over a 2-year period (2004–2005)
From page 46...
... SECTION V -- DESCRIPTION OF STRATEGIES Objective 18.2 C -- Reduce the Severity of Median Barrier Crashes That Occur This section includes a strategy aiming at the likelihood of reducing the severity of the crash rather than preventing the crash. Strategies that are directed at roadside design range from very costly to relatively inexpensive.
From page 47...
... signs or some lighting supports) , placement of objects serving as protection from more hazardous immovable objects or situations (including guardrails and median barriers)
From page 48...
... SECTION V -- DESCRIPTION OF STRATEGIES V-39 EXHIBIT V-18 Strategy Attributes for Improved Design and Application of Barrier and Attenuation Systems (T) Attribute Description Technical Attributes Target Expected Effectiveness Keys to Success Potential Difficulties Appropriate Measures and Data Associated Needs Organizational and Institutional Attributes Organizational, Institutional and Policy Issues Issues Affecting Implementation Time Costs Involved Training and Other Personnel Needs Legislative Needs The target for this strategy is existing safety hardware (guardrail terminals, impact attenuators, and barriers)
From page 49...
... Objective 18.2 D -- Enhance Enforcement and Awareness of Traffic Regulations Strategy 18.2 D1 -- Designate "Highway Safety Corridors" (T) Agencies experiencing significant cross-median collisions on a freeway or expressway corridor may sometimes choose an expensive infrastructure solution such as median barrier placement.
From page 50...
... SECTION V -- DESCRIPTION OF STRATEGIES of reducing the number of collisions, injuries, and fatalities on the highway. Typically though, the common factors used to establish a safety corridor are safety history and community support.
From page 51...
... is no longer required. For example, in the state of Oregon, once a safety corridor's 3-year fatal/serious injury crash rate drops below 110 percent of the state average, then the corridor is decommissioned unless a local stakeholder group "adopts" the corridor at their own expense and continues to provide a meaningful local level of resources.
From page 52...
... SECTION V -- DESCRIPTION OF STRATEGIES somewhat limited in many cases, and therefore any observed reductions in crashes may be due to other reasons, or simply due to the random variation in crashes. Also in some cases, no measurable safety improvement has been recorded.
From page 53...
... Crash information should be available for analytical purposes within a useful time frame for identifying crash problems within a State -- preferably within 90 days of crash. Consistency Crash information should be consistent among reporting jurisdictions within a state.
From page 54...
... SECTION V -- DESCRIPTION OF STRATEGIES Apart from the state-maintained crash data systems, there are federally maintained crash databases like FARS. For the proper evaluation of any of the strategies described, before and after accident study is required to evaluate effectiveness.
From page 55...
... • Work Zone Collisions (Volume 17) • Speed (Not completed)

Key Terms



This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.