9.2 Perceptual and Physical Elements to Support Rural-Urban Transitions

  • When motorists driving at a high speed enter an area with lower speed limits, they tend to underestimate their speed and not adjust it downward enough. The design of transition zones needs to encourage motorists to reduce their speed. Establishing an approach zone upstream of a transition zone is valuable for warning motorists about downstream speed reductions. Physical design measures are the most effective, but they can also be the most hazardous for vehicles traveling at high speeds. Table 9.1 lists design guidelines for different transition zone areas.
Table 9.1 Design Elements for Rural – Urban Transitions
Transition Zone Area Recommended Measures
Rural Area with High Speed Limit
  • None




Approach Zone
  • Use warnings and psychological measures:
    • Advance signing
    • Converging chevrons
    • Optical speed bars
    • Variable message signs
    • Colored pavement
    • Transverse pavement markings




Transition Zone
  • Use physical measures:
    • Speed feedback signs
    • Narrow roads
    • Raised medians
    • Stepped-down speed limits
    • Roundabouts
    • Road reconfigurations


Developed Area with Low Speed Limit
  • Place a gateway treatment where the developed area begins.
  • Measures that are more conspicuous and aggressive (e.g., mini roundabouts, raised speed tables) produce larger reductions in speed and crash frequencies than more passive measures like gateway signs.
  • Use design elements to clearly indicate the relationship between speed limits and changes in road character.
  • There is no one-size-fits-all solution. Make design choices attuned and responsive to local contingencies. But ensure that design elements do not impede user visibility or function as obstacles.

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CONTACT:

Chris VanDyke

Research Scientist | Program Manager

chrisvandyke@uky.edu