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Chapter 2
Design Controls and Criteria

Design Vehicles
Older Drivers
Design Speed Definition
Highway Capacity
Access Control and Access Management
The Pedestrian

Design Vehicles

Four classes of design vehicles:

Design Vehicle

Buses Added



  • Turning templates revised
    • Autoturn
    • Centerline turning radius added
  • Revised symbols
  • Typical dimensions
  • Turning characteristics defined
  • Truck tractors added
Vehicle dimensions and minimum turning path for Interstate Semitrailer WB-19 [WB-62] design vehicle.

Older Drivers

" . . . should be aware of the capabilities and needs of older road users and consider appropriate measures to aid their performance."

Expanded observations

Expanded countermeasures which may help alleviate potential problems

Older Driver Highway Design Handbook


Operating Speed

OLD: highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section - by - section basis

NEW: the speed at which drivers are observed operating their vehicles during free - flow conditions

Design Speed

OLD: maximum safe speed that can be maintained over a specific section of highway when conditions are so favorable that the design features of the highway govern.

NEW: a selected speed used to determine the various geometric design features of the roadway.



Traffic Flow Relationships

Highway Capacity

  • Updated based on HCM 2000
  • Rewritten to eliminate duplication of material
  • Exhibit 2 - 31 Generalized definitions of Level of Service replaces Level of Service Characteristics
  • Refers user to HCM for details
Front cover of the 2000 Highway Capacity Manual

Access Control
Access Management

The Pedestrian


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