Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections (2008) / Chapter Skim
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Pages 5-14
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From page 5... ...
The Guidelines focus on speed reduction treatments within an intersection's geometric and operational influ5 S E C T I O N 2 Speed Considerations
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The need for speed reduction at intersections can be considered in the following general conditions: • The posted speed of the segment is higher than the desired speed of the intersection approach (e.g., the intersection approach is stop controlled, or a transition from a rural to a more urbanized environment occurs at the intersection)
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High speeds generally are associated with long trips, and low speeds generally are associated with short trips or with facilities that have more frequent access. Posted speeds frequently correlate with these intended uses.
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This affects the length of alignment tapers, bay tapers, and the deceleration components of turn-lane designs. 2.4.2 Quality and Comfort of the Roadway Environment The function of roadways and intersections must be balanced with the needs of adjacent land uses to both maintain environmental quality and to provide necessary mobility.
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In addition, the greater a vehicle's speed, the less time there is for other motorists, bicyclists, or pedestrians to react to, and avoid, that vehicle. Thus, although there is no research to support the common assumption that reducing speeds will reduce crash frequency, reducing speed variation may achieve this.
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The speed adaptation hypothesis states that the perceived speed of one's vehicle will be lower than the actual speed if the driver has recently operated the vehicle at a higher speed. 10 Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections
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Lane widths, horizontal/vertical geometry, sight distance, curbs, and bike lanes may influence measured speeds and desired speeds. Conflicts and As the distance between points of friction Friction (driveways, intersections, pedestrian crossings, lane drops)
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2.6 Conditions Potentially Sensitive to Speed This section identifies a variety of conditions, elements, and data that may indicate that an intersection is particularly sensitive to speed. In some cases, these are contextual considerations 12 Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections Intersection Variable Potential Relationship to Speed Traffic A signalized intersection, a stop-controlled Control/Approach Type intersection, and a yield-controlled intersection require different driver tasks and operating speeds.
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. 2.6.2.2 Driver Behavior Undesirable driver behavior, such as lack of compliance with signals or stop signs, may indicate that excessive speeds approaching an intersection do not give drivers enough time to see and react to traffic control.
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Understanding how speed affects intersection conditions and how those conditions affect speed is considered first to evaluate and select an appropriate speed reduction treatment. 14 Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections
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