This document discusses intersections and their design. It defines an intersection as the area where two roads cross each other, noting they concentrate travel and involve conflicts between motor vehicles, bicycles and pedestrians. The document outlines requirements for intersection design including safety, adequate capacity, visibility and minimizing delays. It discusses basic design considerations like human factors, traffic needs, physical elements and economics. It also defines intersection terminology, types of movements, conflict points, signalization approaches, and types of intersections such as three-way, four-way and multi-leg intersections as well as interchanges.

1. INTERSECTION
Prepared by: Zakir Hussain Farahmand
Under the Supervision OF: Eng. Malyar Talash
Road Design Engineer/NRAP/MoPW
Kabul-Afghanistan
Emails: tmalyar@yahoo.com malyar@nrap.gov.af
Mob: 0093786575033

2. Introduction:
 Area which two roads cross each other.
 Key Feature of Street:
 Focus of Activity: concentration of
travel Destinations.
 Conflict Movement: Motor vehicle,
bicycle, pedestrian
 Traffic Control: Cause Delay
 Capacity: reduced by delay

3. Terminology of Intersection

4. Requirement of Intersection
1. Safe and convenient operation for all road users, including
cyclists and pedestrians
2. Adequate capacity for peak-hour demand on all movements;
3. Adequate visibility of conflicting traffic;
4. Minimum delay and disutility to all road users
5. Proper drainage of storm water;
6. Necessary regulatory, warning and informational messages for all
road users;

5. Basic Element Consideration
 Human Factors: like Decision and Reaction time, pedestrian
use and habits and etc.
 Traffic Consideration: like Design and Actual Capacities,
Vehicle speeds, variation of movement, Bicyclic and
pedestrian movements and etc.
 Physical Elements: like Vertical alignments at the
intersection, Sight distance, Angle of the intersection,
Conflict area, Geometric design features, Lighting equipment,
Safety features
 Economic Factors: cost of improvement and energy
consumption.

6. Basic Concept of Intersection
Movement: in a four leg intersection 12 movements exist.
(see the figure}

7. 2- Type of Movements:
 Unopposed Movement: Don’t be any other movement in
opposite. Like Movement on one side.
 Protected Movement: Red signal protect it from opposite
conflict. Left Turn
 Permitted Movement: By considering priority right turning
is allowed. Like Right Turning in respect to Pedestrian footfall
 Prohibited Movement: sometimes in peak hour left turning
is proscribed.

8. Turning Conflict Points
Diverging: points which separate from a road.
Merging: Points which movement approach to a road
Crossing: Points which two opposite movement cross each
other.

9. Signalized intersection
Phase: Unit time which control one or more similar movements come one
after another.
Ring Diagram: Group of phases which separate crossing
movements.

10. Red Clearance: Time which a vehicle inside intersection can pass safely.

11. Type of Intersection
1- At-Grade Intersection
 Three Leg:

12.  Four Leg Intersection:
 Multi- leg intersection:

13. 2- Two level Crossing or Interchange
While two main road cross each other with high volume Traffic
Then at grade intersection changes to interchange

14. References:
• Highway Capacity Manual, Transportation Research Board,
Washington, D.C.2010.
• A Policy on Geometric Design of Highways and Streets, AASHTO,
2011.
• Florida Intersection Design Guide 2015

15. THE END
THANKS FROM ATTENTION