Measuring, Characterizing, and Reporting Pavement Roughness of Low-Speed and Urban Roads (2019) / Chapter Skim
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Pages 26-48
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From page 26... ...
26 This chapter presents the results from an experiment that was conducted to demonstrate the effects of potentially adverse operational conditions on the measurement of longitudinal road profile by high-speed inertial profilers. The experiment included staged reproductions of common operational conditions encountered while conducting network-level profile measurements on urban and low-speed roadways, including operation at low speeds, acceleration and deceleration, stopand-go operation, profiling from a dead stop, and operation on a curve.
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27 vehicle body where the accelerometer is mounted, and Ax is the rearward acceleration. In perfect operation, the pitch angle (θ)
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28 made at various speeds over a rough patch on an urban street. Profiler A measures the profile at 40 mi/hr (64 km/hr)
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29 filtering. The data from Profiler 1 and Profiler 2 were submitted without high-pass filtering.
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30 collection, accelerate to a target final speed, and continue at the final speed to the end of the section. • On the curved section, data collection was performed at several constant speeds using cruise control if it was possible to set the cruise control to the desired speed.
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31 running from 262.5–1378.0 ft (80–420 m) from the start of the section and in the right wheel path over a range running from 65.6–1378.0 ft (20–420 m)
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32 Figure 35 shows the roughness profile over the second transversely inconsistent area. Here, the third pass at 30 mi/hr (48 km/hr)
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33 110.6, and 112.0 in/mi (1.761, 1.746, and 1.767 m/km) in the right wheel path.
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34 score for comparison of passes at each combination of speeds. Diagonal entries provide the average agreement score for comparisons of repeated runs at the same speed.
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35 3.4.4.1 Characterization of Speed Profiles The strength of the disturbance caused by braking was quantified for each run using speed profiles derived from data recorded by the GPS data logging system. Figure 40 shows a sample speed profile that was recorded during a pass by Profiler 4 with a target deceleration of 0.2 g from an initial speed of 30 mi/hr (48 km/hr)
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36 High-pass filtering modified the spurious content caused by braking. Figures 42 through 45 compare profiles from a pass with braking to three passes at constant speed by the four profilers that applied high-pass filtering (Profilers 3, 4, 5, and 6)
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37 Figure 42. Raw profile trace with braking at 0.28 g, Profiler 4.
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38 The figure shows that the effects of braking on the IRI are localized. The braking with an average deceleration of 0.32 g began at 644.7 ft (196.5 m)
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39 (1 m/km) is spread out over a 0.1-mi (160.9-m)
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40 revealed no effects on the IRI near the onset or termination of acceleration. This indicates that the staged acceleration events did not affect profile content in the range of wavelengths that affect the IRI.
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41 3.4.6.1 Effects on Raw Profiles The time spent without movement during the stop introduced artificial content into the profiles beyond the effects for braking and acceleration. The accelerometer is typically not oriented precisely vertically after the profiler host vehicle comes to rest.
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42 filtering spread out the effect of the step change in elevation at the stop over the same distance in each direction and in proportion to the filter cut-off or base length. Profiles submitted by Profiler 6 with high-pass filtering spread out the influence of stops in a similar fashion.
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43 Figure 54. Elevation profile measured by Profiler 5 with a stop.
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44 In the 12 passes by Profiler 2 with a stop, localized roughness appeared in the short-interval roughness profile with peak values of 3,041–6,273 in/mi (48–99 m/km) on the left side and 0–2,218 in/mi (0–35 m/km)
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45 3.4.7 Operation from a Dead Stop In these tests, the profiler operators were asked to initiate profile data collection while the profiler was stationary, and then accelerate to 45 mi/hr (72 km/hr) and maintain this speed until the end of the section.
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46 3.4.8 Operation on a Curve These runs were intended to examine errors in profile caused by lateral acceleration and changes in lateral acceleration on a curve. Passes over a section with a short curve to the right followed by a long curve to the left were conducted at 20, 30, and 40 mi/hr (32, 48, and 64 km/hr)
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47 not as well repeated at various speeds by Profiler 1 as they were on the tangent section. This was true of all six inertial profilers and was due in part to less consistent lateral tracking and less consistent measurement of longitudinal distance on the curves.
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48 and the wheel rotates less for the same travel distance. The resulting reduction in tire rotation relative to the free-rolling condition causes it to register a smaller distance for the same amount of travel.
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