Speed Reduction Techniques for Rural High-to-Low Speed Transitions (2011) / Chapter Skim
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Pages 58-73
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From page 58... ...
56 CHAPTER FOUR HIGH-TO-LOW SPEED TRANSITION TOOLBOX • The relative cost of implementation (i.e., high, moderate, low) • Possible impacts and cautions concerning the measure • Basic literature references.
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From page 59... ...
57 EFFECTIVENESS Medians have been shown to be very effective in lowering operating speeds, particularly when they create a deflection in the vehicle path. Berger and Linauer (1998)
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58 TREATMENT Roundabout CATEGORY Geometric design COST High DESCRIPTION A one-way circular intersection that is characterized by a splitter island on all approaches and entering motorists yielding the right-of-way to motorists already on the circular roadway. EFFECTIVENESS Rodegerdts et al.
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59 U.S. CUSTOMARY: Where: Vexit = the predicted exit speed for the roundabout (mph)
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From page 62... ...
60 TREATMENT Road or Lane Narrowings CATEGORY Geometric design COST High DESCRIPTION Any form of narrowing the road platform, including lane narrowing from the road edges or through the introduction of a raised or painted median. EFFECTIVENESS Charlton and Baas (2006)
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From page 63... ...
61 TREATMENT Road Diets CATEGORY Geometric design/traffic control COST Medium to High DESCRIPTION A reduction in the number of travel lanes for motorized traffic, with the excess road space generally reallocated to bicycle lanes, painted medians, or center turn lanes. Source: http://www.tfhrc.gov/safety/hsis/pubs/04082/index.htm EFFECTIVENESS Knapp and Rosales (2007)
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From page 64... ...
62 TREATMENT Chicanes or Horizontal Deflections CATEGORY Geometric design COST Medium to High DESCRIPTION Introducing horizontal deflections and shifts in the alignment of the road that require motorists to slow down as they negotiate the road. Source: San Francisco Municipal Transportation Agency (www.sfmta.com/cms/ocalm/13567.html)
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From page 65... ...
63 TREATMENT Countdown Speed Signs/Markers CATEGORY Traffic control devices COST Low A longitudinal series of three traditional speed limit signs that are complemented with rectangular signs mounted below the speed limit signs. The complementary sign is a white background with one, two, or three diagonal slashes.
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From page 66... ...
64 TREATMENT Speed Feedback Signs CATEGORY Traffic control devices COST Medium DESCRIPTION Electronic signs placed at the roadside are connected to a device that measures the speed of approaching vehicles and displays the actual travel speed to motorists. Source: Richard Drdul EFFECTIVENESS Donnell and Cruzado (2008)
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From page 67... ...
65 TREATMENT Speed-Activated Speed Limit Signs CATEGORY Traffic control devices COST Medium DESCRIPTION Electronic signs placed at the roadside that are connected to a device that measures the speed of approaching vehicles. Should the measured speed exceed the legal speed limit, then the electronic sign is activated to display the legal speed limit.
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From page 68... ...
66 TREATMENT Transitional Speed Limits (or Stepped-Down Speed Limit) CATEGORY Traffic control devices COST Low DESCRIPTION Provision of an intermediate or stepped-down speed limit to ease the transition from a high-to-low speed area.
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From page 69... ...
67 TREATMENT Removal of Pavement Markings CATEGORY Traffic control devices COST Medium DESCRIPTION Removing the directional dividing line and/or the edge lines from the pavement surface to create discomfort for motorists, causing them to slow down commensurately. Source: Kennedy (2005)
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From page 70... ...
68 TREATMENT Optical Speed Bars CATEGORY Traffic control devices COST Low DESCRIPTION Transverse markings placed in and across the travel lane with the intent of increasing the optical flow of information and creating a sense of increasing speed. The speed bars may be evenly spaced or exponentially spaced with a decreased spacing as one travels downstream.
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From page 71... ...
69 TREATMENT Speed Humps, Raised Crosswalks, Raised Intersections, and Vertical Deflections CATEGORY Surface treatment COST Medium to High DESCRIPTION A relatively abrupt change in the elevation of the road surface so as to create an uncomfortable feeling for motorized traffic when the feature is traversed at a high speed. Source: Richard Drdul EFFECTIVENESS Vertical deflections at high-to-low speed transitions have not been used extensively in practice because the profession is wary of the potential for vehicle damage and lost control crashes resulting from a motorist striking the deflection at full speed.
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From page 72... ...
70 TREATMENT Rumblewave Surfaces CATEGORY Pavement surface treatment COST Medium to high DESCRIPTION An undulating road surface that resembles a series of closely spaced speed humps using a sinusoidal profile. The amplitude of the waves are about one quarter of an inch, and the wavelength is in the order of 1.1 feet.
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From page 73... ...
71 TREATMENT Gateway CATEGORY Roadside features COST Low to High DESCRIPTION Measures and elements that are placed at the urban/rural threshold and collectively present a visual cue to the driver that this is the point of change in roadway character. Gateways can consist of a simple sign at the roadside, a raised island, or an elaborate collection of measures including freestanding structures placed over/across the traveled way, colored pavement, and pavement markings.
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