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Section 2: Condition Diagram

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Introduction

A study should be made of existing conditions at the study location and along each approach to it. Where the location is open to traffic, the study should include existing traffic control devices (signs, signals, markings, speed zones, etc.).

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Information Sources

The condition diagram should provide a complete presentation of the physical layout of the study location as it currently exists.

Plan Sheets from Prior Projects. Final construction plan sheets from prior projects may be used as a basis for the condition diagram.

Aerial Photographs. The Information Systems Division (ISD) will prepare, on request, the condition diagram from aerial photographs. However, due to the expense of obtaining aerial photographs, districts seldom make this request. ISD prepares condition diagrams at scales shown in the following table.

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English Scale

Approximate Metric Equivalent Scale

1 inch = 20 feet

1:200

1 inch = 50 feet

1:500

1 inch = 100 feet

1:1000


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Additional Necessary Information

The following items should be included in the condition diagram:

  • north cardinal direction
  • highway and intersection design features, including:
    • pavement edges, curbs, and shoulders (unpaved or paved)
    • widths of approaches
    • approach grades
    • channelization
    • parking conditions and restrictions
    • bus stops
    • safety lighting or continuous lighting
    • any other roadway features which may affect traffic operations
  • roadside development, including:
    • sight distance restrictions (trees, bushes, advertising and other signs, poles, fences, bridge, and guard rails)
    • off street parking
    • driveway locations
    • utility and other poles
    • adjacent land use
    • any other pertinent features
  • traffic control devices, such as:
    • signs
    • traffic signals (type, face locations, etc.)
    • distance to adjacent traffic signals within 1.61 km (one mile) (indicate if none)
    • pavement markings
    • any other traffic control devices
    • railroad crossing and type of control
    • distance to railroad from traffic signal.
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