13.2.1 Intersection Characteristics

An intersection includes the areas needed for all modes of travel that use the intersection. These modes of travel include:
  • Bicycle/Micromobility;
  • Wheelebase (WB);
  • Pedestrian;
  • Truck (WB Trucks, Recreational Vehicles, etc.); and
  • Transit (School Bus, City Bus, Trains, etc.).
Therefore, the intersection design not only addresses the roadway pavement, but the adjacent sidewalks, pedestrian curb ramps, bicycle facilities, speed-change/auxiliary lanes, medians, and islands. Intersections are a key feature of roadway design in four respects:
  • Focus of Land Use Activity –
    The land near intersections often contains a concentration of travel destinations that are accessed by multiple modes of transportation. This is especially true for intersections in the Urban and Urban Core Contexts.
  • Conflict Points –
     Pedestrians, bicyclists, and motor vehicles often cross paths at intersections where through and turning movements conflict. These crossings are referred to as “conflict points” and can be further categorized by movement type and severity.
  • Traffic Control –
     Movement of users may be assigned through use of traffic control devices such as yield signs, stop signs, and traffic signals.
  • Capacity –
     Traffic control at intersections will often limit the number of users that can be accommodated within a given time period on intersecting roadways.
Figure 13-1
shows the number and type of motor-vehicle conflict points at typical four-leg, three-leg, and roundabout intersections. Conflict points should also be considered when locating driveways along a roadway. Providing separation between driveways reduces the potential for collisions by reducing the number of conflict points and increasing the distance between conflict points. See
Chapter 16
and refer to TxDOT’s
AMM
for additional information on driveway spacing requirements and driveway design.
Conflict Points at Various Intersection Types ( click in image to see full-size image)
Figure 13-1: Conflict Points at Various Intersection Types
Source: AASHTO’s A Policy on Geometric Design of Highways and Streets