00818867

Component

https://doi.org/10.3141/1751-11

http://scholar.google.com...anov&publication_year=2001

Ramp facilities provide all freeway entrance and exit opportunities. Thus, excellent freeway ramp design criteria are critical to freeway operations and safety. Current freeway entry ramp design speed criteria were evaluated by observing six (nonloop) ramps in three Texas cities. Ramp and freeway traffic speed-distance relationships were observed in the field using videotaping methods. Traffic operations were described in terms of ramp and freeway speeds and accelerations, as well as merging locations, accepted time gap sizes, and freeway time headways. Performance characteristics for numerous ramp features and volume combinations were compared. Combined design feature and traffic volume effects on freeway operations and both positive and negative impacts that may be attributed to ramp design features were evaluated. Several notable conclusions were reached. First, for virtually all observations, ramp driver speeds were found to be greater than 50% of the freeway design speed; therefore, a 50th percentile design speed might have negative safety implications. Second, the ability of entry ramp drivers to see freeway right-lane traffic, into which merging is intended, before reaching the ramp gore was found to be very important. Therefore, the AASHTO acceleration lane length measurement model for taper-type ramps should be clarified. The acceleration lane should be considered to begin only when ramp drivers have an unobstructed view of freeway right-lane traffic.

This paper appears in Transportation Research Record No. 1751, Geometric Design and the Effects on Traffic Operations 2001.

English

p. 90-100

2001

Transportation Research Record

0309072123

Figures (6) ; References (4) ; Tables (1)

Acceleration (Mechanics); Acceleration lanes; Design; Design speed; Field studies; Freeways; Gap acceptance; Headways; Interchange ramps; Length; Merging area; Traffic speed; Traffic volume; Videotapes

Speed distance relationships

Texas

Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Oct 18 2001 12:00AM

• APPLICATION OF ARTIFICIAL NEURAL NETWORKS TO PREDICT SPEEDS ON TWO-LANE RURAL HIGHWAYS
• CONTROLS FOR HORIZONTAL CURVE DESIGN
• DESIGN FACTORS THAT AFFECT DRIVER SPEED ON SUBURBAN STREETS
• GEOMETRIC DESIGN AND SAFETY ASPECTS OF ROUNDABOUTS
• GUIDELINES FOR OPPOSING LEFT-TURN LANE-LINE WIDTHS
• OPERATING SPEED PREDICTION ON CREST VERTICAL CURVES OF RURAL TWO-LANE HIGHWAYS IN NEBRASKA
• SAFETY EFFECT OF ROUNDABOUT CONVERSIONS IN THE UNITED STATES: EMPIRICAL BAYES OBSERVATIONAL BEFORE-AFTER STUDY
• SPEED BEHAVIOR ANALYSIS AT CURVED RAMP SECTIONS OF MINOR INTERCHANGES
• SPEED PREDICTION MODELS FOR TRUCKS ON TWO-LANE RURAL HIGHWAYS
• TRAVEL TIME COMPARISONS BETWEEN SEVEN UNCONVENTIONAL ARTERIAL INTERSECTION DESIGNS