These charts are comprehensive but are not the only solutions possible. Both of these guides start with identified problems and use charts to match potential solutions to the identified problems. Any information contained in these documents is considered secondary to the EPG. Both of these documents should be used as reference tools only. The selection of countermeasures is covered in AASHTO's Highway Safety Manual and NCHRP 500 series. For most routes, a crash rate is considered poor when it starts to reach double the statewide average.Ĭrash Modification Factor (CMF) Clearinghouse presents proven countermeasures, the most important of which show up in the HSM It is also important to compare routes by urban/rural classifications. For instance, a rural county lettered route functions differently from Rte. Comparisons by roadway type are a better indication of a roadway’s safety than comparisons by route designation. Typically, non-intersection studies are compared by roadway type. When calculating crash rates during the analysis, compare the calculated rate to the statewide rate. A collision diagram helps to identify crash patterns. When performing a crash analysis, look for crash patterns that may lead to easily recognizable countermeasures. A location with severe crashes should be reviewed for sight distance, signing, signal timing or other roadway features that may be leading to improper driver behavior. A high number of crashes having no severe crashes typically indicates a location with high traffic volumes and a potential capacity or operational issue. Crashes are reviewed for severity level of crashes as well as total number of crashes. Crash information is obtained during the data collection phase of the traffic study. TMS has a highway capacity analysis tool.Ī crash analysis is performed for a traffic study to determine whether a safety or operational problem exists. The HCM provides methodologies for calculating capacity for ![]() 14.3 905.2.14.3 Additional Guidelines for Establishing Speed LimitsĪccording to the Highway Capacity Manual (HCM), the capacity of a facility is the maximum hourly rate that persons or vehicles can reasonably be expected to traverse a point or uniform section of a lane or roadway during a given time period under prevailing roadway, traffic and control conditions.14.2.6 905.2.14.2.6 Procedures for Obtaining Prevailing Speed Data.14.2.2.1 Table 905.2.14.2.2 Prevailing Speed Reduction for Total Crash Rates.14.2.1.1 Table 905.2.14.2.1 Prevailing Speed Reduction for Severe Crash Rates.14.2.1 905.2.14.2.1 Fatality and Disabling Injury Crash Rate. ![]() 14.2 905.2.14.2 Prevailing Speed Determination. ![]()
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