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1 Road maintenance and construction Hossein Naraghi CE 590 Special Topics Safety March 2003 Time spent: 6 hrs.

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Presentation on theme: "1 Road maintenance and construction Hossein Naraghi CE 590 Special Topics Safety March 2003 Time spent: 6 hrs."— Presentation transcript:

1 1 Road maintenance and construction Hossein Naraghi CE 590 Special Topics Safety March 2003 Time spent: 6 hrs

2 2 Pavement condition Pavement condition includes Resistance of the pavement surface Important in crash terms Roughness of the pavement Important in terms of economic efficiency Effects on vehicle operating costs Road maintenance activities which involve resurfacing may be directed at either friction or roughness, or both

3 3 Pavement condition (continued) Skid resistance Skidding is a contributory factor to many crashes On wet roads On approaches to intersections Crashes which occur in wet weather typically Occur at 2 to 3 times the rate of crashes in dry weather, all else being equal Represent about 20-30 percent of total crashes Involve skidding In up to 70% of cases, improving skid resistance may be helpful

4 4 Pavement condition (continued) Skidding crashes include Rear-end Run-off-road Sideswipe Head-on Pedestrian Coefficient of friction Above 0.55 is usually enough to significantly reduce braking and turning crashes

5 5 Pavement condition (continued) Frictional resistance can be substantially improved by Providing a suitable road surface texture Overlay of high friction asphalt Grooving/grinding an existing surface The need for such a treatment can assessed by measuring friction using skid resistance machines

6 6 Pavement condition (continued) Moisture presence has Little effect on skid resistance at low speeds Much higher effect at higher speed As speed increases the water must squeeze away from the surface before the tire can grip Hydroplaning s more likely at higher speeds Tire does not develop full grip over an area because of the presence of a film of water about 6 mm thick

7 7 Pavement condition (continued) Splash and spray which associated with crashes occurrence Related to heavy vehicles on wet roads Can be reduced through the use of open-graded or porous asphalt This is much less noisy than regular asphalt or concrete surfaces Mainly controlled through on-vehicle devices

8 8 Pavement condition (continued) Considerable attention has been given to the effects of road roughness on vehicle operating costs and to the economic efficiency of road provision and optimum maintenance intervention levels Less attention has been given to safety aspects of road roughness Might be due the reason that in developed countries at least, roads are maintained at a sufficiently high level that roughness does not become a safety issue

9 9 Pavement condition (continued) Surface roughness is a much larger factor in truck crashes and motorcycle crashes than in car crashes An Australian study of truck crashes found that 10.7% of such crashes associated with drivers losing control due to potholes Some cases in US reported failure of a mechanical component of the truck was due to pavement roughness Another study found that rough surfaces can cause load shift in large trucks, or rollover or both

10 10 Pavement condition (continued) It seems reasonable to suppose that Irregularities or defects in the road surface could adversely affect the ability of driver to control the vehicle There is a little research on the subject In developed countries this factor affecting only a small percentages of crashes This factor is affecting a more significant percentages of truck crashes

11 11 Pavement resurfacing Pavement resurfacing may be undertaken as part of an crash-related mass action program or part of routine pavement maintenance The potential effect of resurfacing on safety is a result of two factors working in opposite direction Since resurfacing reduces surface roughness and improves ride quality, it may lead to increase in average speed Resurfacing often increases pavement skid resistance, which reduces stopping distance and improves vehicle controllability when pavement surface is wet

12 12 Pavement resurfacing (continued) Safety effects of resurfacing Routine resurfacing of rural roads increases dry weather crashes by 10% Increased speeds Dry weather skid resistance and stopping are unaffected by resurfacing unless the original pavement was extremely rough For most rural roads, the net effect of resurfacing on crash rate is small and gradually diminishes over time

13 13 Pavement resurfacing (continued) Resurfacing improves the safety performance of roads that experience an abnormally high frequency of wet weather crashes Resurfacing provide opportunity to correct deficient pavement cross slope at little or no extra cost Correcting cross slopes allows better drainage of the pavement surface and improves vehicle control in wet weather Careful attention to removal of surface defects and necessary improvements to skid resistance, surface drainage and superelevation may help to offset the adverse effects of increased speeds

14 14 Work zones Data from US suggests that work zones are hazardous from a road safety viewpoint Sites showing the worst increase in crashes were short duration Short term construction zones perhaps reflecting driver expectancy or poor road work signing, or both Heavy vehicles face particular difficulties at work zones include Median crossovers Reduced number of lanes Reduced lane widths

15 15 Work zones (continued) Being required to travel closer to potential hazards Excavations Drop-offs Short merge zones Flashing signals Which are at truck driver’s eye height causing visibility problems All these mean explicit consideration should be given to warning, delineation and control devices for trucks at work zones

16 16 Work zones (continued) Principles involved in safety and effectively controlling traffic at work zones Traffic safety should be an integral and high priority element of every construction job, from planning, through design, to construction Construction and maintenance operations should inhibit traffic as little as possible Clear and positive guidance must be provided to drivers approaching and traversing work zones

17 17 Work zones (continued) Routine inspection of traffic control elements is essential to ensure acceptable traffic safety and operations Appropriate training of all relevant personnel is essential Adequate legislative authority for implementation and enforcement of traffic regulations applicable to work zones Maintaining good public relations, and keeping the motoring public informed is essential

18 18 Work zones (continued) Organization for Economic Cooperation and Development has developed the following guidelines for traffic management at work zones Capacity restriction must be carefully evaluated and monitored Lane closures should normally start from the fast lane Buffer zones should be provided wherever possible Incident control is important, especially with contra-flow techniques Speed limits should be realistic, should be supported by appropriate accompanying measures and not rely solely on signing

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