13.2.4 Design Considerations for Intersection User Groups

The design of intersections should use performance measures and engineering judgement to balance the needs of all roadway users and transportation modes. The size and design of physical elements such as roadway width, lane width, and corner radii are selected according to the volume and priority of each of the intersection user groups.
For an intersection in the urban and urban core contexts, design priority may be given to pedestrians, bicyclists, passenger vehicles, and buses. Basic accommodation may be given to trucks, except for intersections located on truck routes or Freight Network. Intersections in the suburban or rural contexts near industrial and commercial areas may be designed for automobiles and trucks with basic accommodations for pedestrians, cyclists, and transit. Design considerations for users include:
Motor-Vehicles (not including trucks) –
 Key elements affecting intersection performance for motor vehicles are:
  • The type of traffic control;
  • Vehicular Capacity of the intersection (i.e., number of lanes);
  • Ability and Capacity to make turning movements;
  • Visibility of approaching and crossing pedestrians and bicyclists; and
  • Visibility of approaching and crossing motor vehicles.
Bicyclists –
 Key elements affecting intersection performance for bicyclists are:
  • The degree to which the roadway pavement is shared or used exclusively by bicyclists;
  • The relationship between turning and through movements for motor vehicles and bicyclists;
  • Traffic control for bicyclists;
  • The differential in speed between motor vehicles and bicycles; and
  • Conflicts with pedestrian movements
Pedestrians –
 Key elements affecting intersection performance for pedestrians are:
  • The amount of ROW provided for pedestrians use (e.g., sidewalk width);
  • Crossing distance and resulting duration of exposure to motor-vehicle and bicycle traffic;
  • The volume of conflicting traffic;
  • Speed and visibility of approaching traffic;
  • Turning speeds;
  • Permissive right-turn on red;
  • Permissive left turn movements;
  • Accessibility to pedestrians with disabilities; and
  • Traffic Control for Pedestrians
Trucks –
 Trucks share many of the same elements as motor-vehicles described in the preceding sections. In addition:
  • Trucks are typically three or four times the length of other motor-vehicles;
  • May be much slower starting than most motor-vehicles; and
  • May need much larger turning radii than most motor-vehicles.
Therefore, the presence and frequency of trucks affects the capacity of the intersection, the width of the driving surface needed for turning movements, and the radius of turning movements.
Design of intersection elements for one group of users will often affect other users.
 For example, an intersection designed to accommodate trucks with no encroachment into adjacent lanes needs large corner radii, wide turning roadways, and results in greater distances for pedestrians to cross.
In addition to the users of the street and intersections, owners and users of adjacent land often have a direct interest in the intersection design. This interest can be particularly sensitive where the intersection is surrounded by retail, commercial, historic, or institutional land uses. The primary concerns include:
  • Maintenance of vehicular access to private property;
  • Turn restrictions;
  • Landscaping;
  • Driveway access;
  • ROW acquisition; and
  • Provision of convenient pedestrian and bicyclist access.