CHAPTER 2 BARRIER WARRANTS

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Barrier Warrants ________ November 20052.4.2 Strategies for Corrective ActionPossible strategies are summarized in Table 2.7.Table 2.7: Strategies for Corrective ActionsStrategyPossible Corrective ActionsReduce the probability of vehicles leaving Flatten horizontal curvesthe roadway Provide adequate superelevation Provide standard lane widths Pave with a skid-resistant surface Widen shoulders Pave shoulders Mark centerline and edge lines Delineate sharp curves Provide shoulder rumble stripsEliminate the hazard Remove the hazard Relocate the hazard to outside theclear zoneReduce the severity of the hazard Make the hazard crashworthy orbreakaway Shield with a barrierAccept the risk and leave the hazard Delineate the edge of traveled wayunprotected Install object markers on thehazard, if appropriateFigure 2.5: Delineation on a Horizontal Curve________________________________________________________________________2-14 Analyze Strategies
Barrier Warrants ________ November 20052.4.3 Strategies for Specific HazardsOf the severity groups discussed in Section 2.3.1, Group 1 hazards are estimated tohave a severity index of below 3.0 (fatalities are unlikely), Group 2 hazards have aseverity index of 3.0 to 4.9 (some possibility of serious injury and fatality, but probablyless severe than barriers) and Group 3 hazards have a severity index of 5.0 and higher(may be more severe than a crash into a barrier). Currently acceptable roadside barriersare estimated to have a severity index of 4.9. All these severity indices are estimated at100 km/h (62mph), but generally will have the same relative meaning at lower speeds.Group 2 hazards should be considered for the same corrective actions as Group 3hazards if they have crash histories or are located so that a vehicle could strike morethan one hazard in the same run-off-the-road event.The following strategies are generally appropriate for the severity groups identified inSection 2.3:Severity GroupGroup 1Possible Corrective ActionsAccepting the risk and leaving the hazard is usuallyappropriate. Avoid placing these conditions in theclear zone or take simple, low-cost correctiveactions if possible. Group 1 hazards commonly donot justify expenditure of substantial funds tocorrect.Group 2 Consider cost-effective strategies to reduceprobability, eliminate the hazard or reduce theseverity of the hazard. Because these hazardsgenerally do no warrant shielding with a roadsidebarrier, the cost of a corrective action should beless than the expected cost of a barrier. If a newroad, avoid placing Group 2 hazards in the clearzone.Group 3Evaluate for possible use of roadside barriers if it istoo expensive or impractical to eliminate either thehazard or make it crashworthy. If a barrier is foundnot to be warranted or if an alternate treatment isless expensive than a barrier, treat as a Group 2hazard.Solutions can include combinations of strategies. For instance, if a large cross drainculvert headwall is within the clear zone, a combination of effective corrective actionsmight be to improve the shoulders, add edge lines, extend the headwall to outside theclear zone, and remodel the headwall to make it more crashworthy.________________________________________________________________________Analyze Strategies 2-15
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CHAPTER 2 BARRIER WARRANTS

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