Design Guidance for High-Speed to Low-Speed Transitions Zones for Rural Highways (2012) / Chapter Skim
Currently Skimming:
Pages 6-22
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 6... ...
6S e c t i o n 2 This literature review is divided into three sections. The first section presents key findings from NCHRP Synthesis 412 (Forbes, 2011)
|
From page 7... ...
Literature Review 7 The basic principle is that motorists are first provided with warning devices and psychological measures early in the transition zone, and are then presented with physical measures closer to the community. This approach to transition zone design is intended to better satisfy driver behavior and avoid abrupt appearance of a gateway or physical traffic calming feature.
|
From page 8... ...
8 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways Figures 2-2 through 2-6 are effectiveness estimates as summarized in Chapter 4 of NCHRP Synthesis 412 (Forbes, 2011)
|
From page 9... ...
Treatment: Roundabout Description: A roundabout is a form of circular intersection in which traffic travels counterclockwise (in the United States and other right-hand traffic countries) around a central island.
|
From page 10... ...
10 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways Treatment: Center Island/Raised Median Description: A channelizing island that creates separation between the two opposing directions of travel. Center islands/raised medians can create shifts or deflections in the travel paths of vehicles and often reduce the effective widths of the roadways.
|
From page 11... ...
Literature Review 11 Treatment: Road Diet Description: A reduction in the number of through lanes (e.g., converting a four-lane road to a three-lane roadway with a two-way left-turn lane or converting a four-lane roadway to a two-lane roadway with a raised median or on-street parking)
|
From page 12... ...
12 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways Treatment: Speed-Activated Feedback Sign Description: A variety of warning and/or dynamic speed signs that indicate a reduction in the speed limit and alert the driver that he/she is traveling above the posted speed limit for that portion of roadway. Speed Estimate: 6-mph reduction in mean speeds (Donnell and Cruzado, 2008)
|
From page 13... ...
Treatment: Welcome Sign Description: A physical landmark or sign that indicates to drivers that they are entering a community. Welcome signs are generally placed to the right of the roadway, but some may be large enough to span the roadway.
|
From page 14... ...
14 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways 2.3 Summary of International Guidelines Internationally, the use of transition zone treatments is more advanced than in the United States. Several countries have developed guidelines for the use of transition zone treatments along rural routes approaching communities.
|
From page 15... ...
Literature Review 15 • Colored paving materials through the threshold pinch point, and • Size and color of the combined speed limit and place name sign. Nighttime conspicuity of the threshold can be enhanced by using reflectorized paint or reflective strips on all curbs used in build-outs or median islands.
|
From page 16... ...
16 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways Figure 2-9. Typical untreated approach to a community (LTSA, 2002)
|
From page 17... ...
Literature Review 17 Figure 2-10. Completed threshold (LTSA, 2002)
|
From page 18... ...
18 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways The UK guidelines indicate traffic calming treatments need to be visible both day and night, as well as in adverse weather conditions. The effects of traffic calming treatments on drainage and along steep grades is also an important consideration, as some treatments may adversely affect the driving environment.
|
From page 19... ...
Literature Review 19 Figure 2-11. Highway sign in the UK warning drivers of the risks of speeding (IH and TCS, 2005)
|
From page 20... ...
20 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways A cumulative effect can be achieved by a combination of road narrowing and the introduction of trees and other vertical elements, culminating in the gateway. Chosen speeds are found to be lower where the height of the vertical elements is greater than the width of the road.
|
From page 21... ...
Literature Review 21 of central islands on speed has been found to be only moderate, but in addition to speed reduction they also provide the opportunity to build a new, more attractive, urban space by dividing the old street profile. Roundabouts in Germany have been found to provide very effective speed reduction at at-grade intersections.
|
From page 22... ...
22 Design Guidance for High-Speed to Low-Speed transition Zones for Rural Highways • The length of the built-up area is at least 1,300 ft. • Building density (i.e., building frontage related to road length)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.