IIW

STEM Activity: How to layout an intersection?

Roadway intersections are locations where roads meet, and drivers can make turns from one road to another. There are many types of intersections – the simplest involve just two roads at right angles to each other, while more complex intersections may include left/right turn lanes, pedestrian refuge islands, roundabouts, or even 3 or more roadways all meeting at the same location! Intersection design is an essential consideration for roadway projects to keep traffic flowing smoothly to allow cars and even large trucks to make comfortable turns between streets. Civil Engineers use specialized software to layout to intersections for construction, but it is possible to develop a feel for the design process with a few simple tools.

In this activity, students will experiment with the basic principles of intersection layout and how a good design can contribute to roadway safety. Afterward, consider looking at some online maps to find some different types of intersections. Students may want to try and draw some of those as well!

Key Terms

  • Centerline: an imaginary line that divides a road in half, and separates traffic moving in opposite directions. Sometimes lane striping is used to mark the centerline on roads with a lot of traffic
  • Edgelines: The edges of a roadway.
  • Thru Lane: a lane of traffic at an intersection that goes straight through the intersection without turning.
  • Turn Lane: a separate lane of traffic at an intersection located left or right of the thru lanes to separate turning traffic (this helps traffic move more smoothly and safely).
  • Intersection Radius: a widened area at each intersection quadrant providing an additional surface for vehicles to drive on while turning.

Materials

  • 2 sheets of 8.5″ x 11″ paper
  • 1 roll of tape
  • 1 straightedge
  • 1 writing utensil (pencil is recommended)
  • 1 toy car (matchbox car-sized)

 

Activity

Try drawing a basic roadway intersection of your own with these simple steps!

  • Using tape, combine both sheets of paper to make an 11″ x 17″ sheet of paper.
  • Using the straightedge, draw two crossing lines on the paper, in a + shape, splitting the paper into 4 approximately equally sized rectangles. These will be the centers of two imaginary roads.
  • Again using the straightedge, draw the edges of the “roads” by drawing lines slightly wider than the toy car on either side of the first lines drawn (4 new lines total). This creates a roadway intersection.
  • Push the toy car around each of the intersection corners that have been created as if it were driving, using the writing utensil to trace its approximate outer path. Leave a little extra space between the car and the lines being drawn! This will create the turning radii at each corner of the intersection.

  • If a pencil was used to draw most of the lines, erase lines that run through the “intersection” area to visually clean things up a little, leaving only the outer edges and centers of the roads.