Speed Reduction Techniques for Rural High-to-Low Speed Transitions (2011) / Chapter Skim
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6 CHAPTER TWO LITERATURE REVIEW Literature in the field of speed and speed management is abundant. However, the applicability of this literature to rural speed transition areas is limited.
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7 was that there needs to be a distinct and evident relationship between the change to the village speed limit and a change in the road environment. TABLE 2 TRAFFIC CALMING EFFECTS ON 85TH PERCENTILE SPEED IN THE UNITED KINGDOM Inbound at Gateway In Village No Measures in the Village Measures in the Village No Measures in the Village Measures in the Village a)
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8 traffic had slowed down. The majority of residents wanted more to be done.
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9 TABLE 3 THE EFFECTS OF TRAFFIC CALMING ON RURAL ROADS IN THE UNITED KINGDOM Case Descriptions Traffic (ADT) Speed in mph (km/h)
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10 FIGURE 2 Transition zone treatments evaluated in Phase 1 research [Source: Pyne et al.
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11 • Roundels used on the approach to 40 mph (65 km/h) speed limits produced a 3 mph (5 km/h)
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12 • Requiring motorists to reduce speed just prior to leaving the urban area (which may promote a uniform, lower speed throughout the urban area) , and • Preventing motorists entering the urban area from using the opposing lane (anecdotal observations)
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13 • Speed reductions were achieved at all of the gateways. • The mean after speeds were close to the speed limits, but the 85th percentile speeds remained considerably above the speed limit.
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14 FIGURE 6 Effect of perceptual measures in New Zealand [Source: Alley (2000)
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15 the SPEED LIMIT SIGN (R2-1) , that was blanked out and activated by motorists exceeding the speed limit.
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16 Department for Transport (2005)
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17 ter emphasize the start of the village. Speed measurements taken proximate to the gateways revealed that mean speeds were reduced by 4 to 8 mph (6.5 to 13 km/h)
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18 operating speeds. This research only marginally relates to speed management in rural areas through two reported projects.
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19 Data were collected at each treatment site at a location upstream of the dynamic display sign, at a point where the sign is not visible, and adjacent to the dynamic sign where the lowered speed limit begins. After results were collected 1 week, 2 months, 7 months, and 1 year after installation.
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20 R3 = path radius on exit from the roundabout (m) a, b = see Table 13 d3 = distance between the midpoint of the path on the circulating roadway and the point of interest on the exit (m)
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21 Arnold and Lantz (2007) As part of a larger experiment with traffic control devices in rural areas, Arnold and Lantz (2007)
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22 limits outside the transition areas were 55 mph and 60 mph (90 and 100 km/h) , and speed limits in the villages were 25 mph to 35 mph (40 km/h to 55 km/h)
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23 TABLE 15 DESCRIPTION OF TRANSITION ZONE TREATMENTS IN IOWA City (population) Treatment Roadway AADT (veh/day)
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24 Measures of effectiveness were as follows: • Absolute change in speed within the impact zone (km/hΔ) • Δ per meter (Δ/m)
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25 Donnell and Cruzado (2008) Donnell and Cruzado (2008)
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26 The 85th percentile speed on the approaches to the test village was about 55 mph (90 km/h)
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27 Township of Clarington, Ontario, Canada. A single transition zone was shown as an approach to an intersection (the start of the urban area)
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28 These results are interpreted as follows: • The presence of a school/children warning sign had the largest influence on speed transition (the difference between the speed measured at two ends of the transition zone)
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29 FIGURE 18 Colored pavement [Source: Russell and Godavarthy (2010)
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30 The traffic calming designs implemented varied significantly and were classified as follows: A No measures in the village, but use of gateway signing associated with significant markings/colored surface/minor narrowing, and in some cases physical measures at the gateway.
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31 TABLE 24 EFFECTS OF TRAFFIC CALMING ON CRASH OCCURRENCE ON IRISH NATIONAL PRIMARY ROADS (1993 TO 1996) Group Crash Type No.
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32 of the roundels were supplemented with flashing beacons. All of the VAS were located 66 ft to 164 ft (20 m to 50 m)
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33 rumble strips at seven pilot locations. A rumblewave surface is shown in Figure 9.
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34 the before or after periods at treated sites. Property damage only crashes decline in some instances and increase in others.
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35 TABLE 28 STUDY RESULTS FOR ROAD DIETS Researcher Statistical Methods No. of Sites Change in Crash Risk Measure Reduction Huang et al.
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36 DOCUMENTED PRACTICES AND GUIDANCE Australia In an early report concerning better balancing the needs of traffic movement, and the needs of village residents and businesses, Armstrong et al.
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37 FIGURE 23 Minimum widths for urban/rural thresholds [Source: Land Transport Safety Authority (2002)
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38 TABLE 30 SPEED REDUCTION MEASURES FOR DESIRED SPEEDS OF 30 MPH (50 KM/H) OR HIGHER Treatment Road Class Desired Speed AADT Traffic Road Local Road ≥40 mph (60 km/h)
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39 • Prohibition of overtaking in the transition zone, using signs, solid centerlines, and gateway islands • Eliminating or reducing the hard shoulder, using crosshatching inside the edge line to increase the visual effect • Narrowing the carriageway • Provision of rumble strips or rumble areas if speeds are not sufficiently reduced by other measures • Signs with a vertical emphasis • Use of appropriate softscape elements such as trees, shrubs, and grass boulevard treatment, which change in composition and degree of formality along the transition zone into the town • Provision of cyclist and pedestrian facilities • Use of the town sign in conjunction with the area speed limit sign in the design of the gateway. The Irish guidelines also recommend the use of a gateway at the downstream end of the transition zone to mark a change in the character of the surrounding area from rural to urban.
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40 – Trees should be planted at 6 to 12 ft (2 to 4 m) oncenter within each clump.
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41 FIGURE 29 Transition zone for 50 to 63 ft (16 to 19 m) rightof-way [Source: National Roads Authority (2005)
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42 • More complex environments tend to produce lower operating speeds owing to increased cognitive load and perceived risk. • Natural traffic calming such as winding roads and "humpback" bridges can be very effective and more acceptable to drivers.
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43 • The core zone is the area of greater development and activity, which requires slower travel speeds for safety reasons; and • The transition zone, which lies between the approach zone and core area, is where drivers are expected to achieve the necessary speed reduction. FIGURE 33 Standard transition zone landscaping in a built-up, semirural area [Source: National Roads Authority (2005)
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44 terline and the edge line markings to halt somewhere in the transition zone to communicate the downstream change in road function.
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45 In Virginia, the Thomas Jefferson Planning District Commission (2004) has developed the "Design Manual for Small Towns: Transportation and Land Use Strategies for Preserving Small Town Character," similar to the Puget Sound document.
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46 TABLE 32 SUMMARY OF LITERATURE REVIEW ON THE EFFECTIVENESS OF RURAL TRAFFIC MANAGEMENT ON SPEED Researcher No. of Study Sites Measures/Treatment Method of Study Results Van Houten and Van Houten (1987)
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47 Table continued from p.46 TABLE 32 SUMMARY OF LITERATURE REVIEW ON THE EFFECTIVENESS OF RURAL TRAFFIC MANAGEMENT ON SPEED Researcher No. of Study Sites Measures/Treatment Method of Study Results Sandberg et al.
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48 • Introduce cycling and pedestrian facilities • Incorporate town entry sign with area speed limit sign in design of gateway • Provide rumble strips and possibly roundabout if speeds not sufficiently reduced by other measures. The presentation also mentions the following design guidelines for gateways: • Make the gateway conspicuous and the most prominent element in the transition zone • Locate the gateway at the end of the transition zone Chartier provides specific design guidelines for transition zones: • Prohibit passing, using signs, solid center lines, and gateway islands • Phase out paved shoulders • Use transverse pavement markings such as crosshatching, blocks, and dragon's teeth • Narrow lane widths using edge lines • Use road side signs to increase the vertical dimension • Use soft landscape elements such as trees, shrubs, and grass boulevard treatments, which change in composition and degree of formality along the transition TABLE 33 SUMMARY OF LITERATURE REVIEW ON THE EFFECTIVENESS OF RURAL TRAFFIC MANAGEMENT ON CRASH RISK Researcher No.
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49 • Ensure forward visibility over stopping distance for 85th percentile approach speed • Do not obscure intersection sightlines • Consider likely future developments when locating • Place a reduced speed limit sign at the gateway location • Extend roadway lighting, where provided, at least two poles upstream of the gateway • Consider painting curbs on gateway islands and buildouts • Consider lighting gateway signs, particularly on long approaches • Consider coloring or texturing the roadway surface for the length of the gateway • Provide a minimum width of 16.7 ft (5.1 m) between signs at a gateway to accommodate large commercial vehicles • Make gateway signs and lighting poles in center islands demountable and frangible • Avoid sign clutter.
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