Road maintenance and construction

1
Road maintenance and construction
Time spent 6 hrs

• Hossein Naraghi
• CE 590 Special Topics
• Safety
• March 2003

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
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
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
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
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
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
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
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
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
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
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
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
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

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Work zones (continued)

• Being required to travel closer to potential
  hazards
• Excavations
• Drop-offs
• Short merge zones
• Flashing signals
• Which are at truck drivers 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
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
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

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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