The National Academies Press

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From page 1... ... 1 Design Guidance for Freeway Mainline Ramp Terminals The design of ramp-freeway junctions is a critical component in the overall safety performance of a controlled access facility. Interchanges present the greatest safety and operational challenges for drivers on the freeway system, as most freeway crashes occur in the vicinity of interchanges. Read the entire page →
From page 2... ... 2Several key findings from the crash analysis are as follows: • In general, there was no difference between truck crash rates and crash rates for all vehicles at either entrance or exit ramps. The exit ramp configurations where truck crash rates exceeded the overall crash rates by the greatest amount included parclo loop, free-flow loop, and "other" ramps. Read the entire page →
From page 3... ... 3 • Deceleration rates are substantially higher on parallel SCLs than on tapered SCLs. • The conceptual approach used in AASHTO policy for the design of exit ramps, which assumes that drivers decelerate in gear (i.e., coast) Read the entire page →
From page 4... ... 4• Where the deceleration lane length is longer than the recommended minimum length presented in the Green Book, most vehicles decelerate at rates lower than those assumed by the Green Book. This is in varying degrees due to the additional length provided and to vehicles decelerating in the freeway lane prior to initiating the diverge maneuver. Read the entire page →
From page 5... ... 5 volumes. These exhibits will ideally be provided in Chapter 3 of the Green Book because they could be used for more general design purposes, rather than just for acceleration lanes. Read the entire page →

From page 1...

... 1 Design Guidance for Freeway Mainline Ramp Terminals The design of ramp-freeway junctions is a critical component in the overall safety performance of a controlled access facility. Interchanges present the greatest safety and operational challenges for drivers on the freeway system, as most freeway crashes occur in the vicinity of interchanges.

Read the entire page →

From page 2...

... 2Several key findings from the crash analysis are as follows: • In general, there was no difference between truck crash rates and crash rates for all vehicles at either entrance or exit ramps. The exit ramp configurations where truck crash rates exceeded the overall crash rates by the greatest amount included parclo loop, free-flow loop, and "other" ramps.

Read the entire page →

From page 3...

... 3 • Deceleration rates are substantially higher on parallel SCLs than on tapered SCLs. • The conceptual approach used in AASHTO policy for the design of exit ramps, which assumes that drivers decelerate in gear (i.e., coast)

Read the entire page →

From page 4...

... 4• Where the deceleration lane length is longer than the recommended minimum length presented in the Green Book, most vehicles decelerate at rates lower than those assumed by the Green Book. This is in varying degrees due to the additional length provided and to vehicles decelerating in the freeway lane prior to initiating the diverge maneuver.

Read the entire page →

From page 5...

... 5 volumes. These exhibits will ideally be provided in Chapter 3 of the Green Book because they could be used for more general design purposes, rather than just for acceleration lanes.

Read the entire page →

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