Application of Crash Modification Factors for Access Management, Volume 2: Research Overview (2021) / Chapter Skim
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Pages 56-64
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56 Introduction Chapter 2 documented the results of a literature review, and Chapter 3 documented the results of an assessment of existing data sources. This chapter identifies areas where additional research is needed and is feasible.
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Strategy Substrategy CMF Availability Missing CMFs Possible Data Sources Manage location, spacing, and design of median openings and crossovers Create directional median opening No CMFs at 3 or more stars CMFs for corridor and site levels. DTFH61-09-C-00026 Safety Evaluation of Access Management Policies and Techniques (includes data from California, Minnesota, and North Carolina)
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From page 58... ...
Strategy Substrategy CMF Availability Missing CMFs Possible Data Sources Convert two-way to one-way Convert two-way operation to one -way operation 8 CMFs rated 3 stars for site level. CMFs for corridor, intersection, and site levels.
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From page 59... ...
Gap Analysis 59 access management conditions, developing adjustment factors for existing SPFs to capture the effects of access management strategies, and developing CMFs for specific access management strategies. This section presents opportunities to fill primary gaps in CMFs and SPFs related to access management.
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Strategy Substrategy Chapter 10 (Rural 2lane) Chapter 11 (Rural Multi lane)
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From page 61... ...
(continued on next page) Improve cross connectivity Allow vehicles to access adjacent properties without returning to the mainline -- -- -- -Install continuous TWLTL on undivided highway Non-road diet scenarios ü Direct – CMF or SPF adjustment factor available -ü Indirect – Use of Multiple SPFs Possible SPFs available -Road diet scenarios -- -ü Indirect – Use of Multiple SPFs Possible SPFs available -Install non-traversable medians, and accommodate left turns and U-turns Convert traversable median (non-TWLTL)
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From page 62... ...
Manage spacing of traffic signals Establish traffic signal density criteria -- -- -- -Establish traffic signal spacing criteria -- -- -- -Create directional median opening -- -- -- -Install U-turns as an alternative to direct left turns -- -- -- -Regulate median opening density -- -- -- -Regulate median opening spacing -- -- -- -Replace full median opening with median designed for left turns from the major roadway -- -- -- -Manage the spacing of signalized and unsignalized access on crossroads in the vicinity of freeway interchanges Establish spacing criteria for interchange ramp terminals -- -- -- -Provide adequate sight distance at access points Manage design elements to improve sight distance -- -- -- -Manage the location and placement of parking (e.g., replace curb parking with offstreet parking or restrict onstreet parking near driveways or intersections to improve sight distance) -- -- -- -Manage vegetation to improve sight distance (e.g., in landscaped medians or sight triangles)
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From page 63... ...
Gap Analysis 63 Install Roundabout at Roadway Intersection The effect on safety of converting an intersection to a roundabout can be inferred from the SPFs available. Roundabout SPFs have been developed in NCHRP Project 17-70 and will be included in the Highway Safety Manual (2nd Edition)
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From page 64... ...
64 Application of Crash Modification Factors for Access Management Replace Two-Way Left-Turn Lane with Non-Traversable Median SPFs in Chapter 12 of the Highway Safety Manual (1st Edition) can be used to infer a CMF by comparing the prediction for a four-lane road with a TWLTL (5T)
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