DESIGN CONSIDERATIONS - 3.1

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Published on 7:03 PM Category:


FUNDAMENTALS OF DESIGN
1. Traffic loading (volume and weight)
2. Soil-support capability (including drainage considerations)
3. Material specifications (aggregate and asphalt)
TRAFFIC
Because the primary function of a pavement is to transmit and distribute wheel loads of vehicles to the supporting sub-grade, information about the traffic stream is required. Pavement must be designed to serve traffic needs over a period of years. Therefore, the volume of traffic and the various types of vehicles using the facility must be estimated for the pavement’s anticipated life.

 A traffic assignment is made based on: (1) historic records of traffic volumes on comparable types of highways and the anticipated function of the highway under consideration, and (2) the percentage of trucks.

 The traffic analysis procedure determines the repetitions of an equivalent single axle load (ESAL). This parameter is defined as the equivalent number of applications of an 18,000-pound, single-axle load during the pavement’s design life. The effects of truck traffic on a pavement can be dramatic.

TRAFFIC CLASSIFICATIONS

Class I
(Very Light) Less than 50 autos per day, less than 7,000 heavy trucks expected during design period.
  • Parking lots, driveways
  • Light traffic farm roads
  • School areas and playgrounds
  • Seasonal recreational roads
  • Sidewalks and bicycle paths
  • Golf cart paths
  • Tennis courts
Class II
(Light) Up to 200 autos per day, 7,000 to 15,000 trucks expected during the design period.
  • Residential streets
  • Rural farm roads
  • Parking lots of less than 500 stalls
  • Airports - 7,500 pound maximum gross weight
Class III
(Medium) Up to 700 autos per day, 70,000 to 150,000 trucks expected during design period.
  • Urban minor collector streets
  • Rural minor collector streets
  • Parking lots - more than 500 stalls
  • Airports - 15,000 pound maximum gross weight.
Class IV
(Medium) Up to 4,500 autos per day, 700,000 to 1,500,000 trucks expected during design period.
  • Urban minor arterial and light industrial streets
  • Rural major collector and minor arterial highways
  • Industrial lots, truck stalls
  • Bus driveways and loading zones
  • Airports - 30,000 pound maximum gross weight.
Class V
(Heavy) Up to 9,500 autos per day, 2,000,000 to 4,500,000 trucks expected during design period.
  • Urban freeways, expressways and other principal arterial highways
  • Rural interstate and other principal arterial highways
  • Local industrial streets
  • Major Service drives or entrances
  • Airports - 60,000 pound maximum gross weight
Class VI
(Very Heavy) Unlimited autos, 7,000,000 to 15,000,000 trucks expected during design period.
  • Urban interstate highways
  • Some industrial roads
  • Airports - over 60,000 pounds maximum gross weight