Intersection Sight Distance Case C1 Ryan Miller CE 480 10/19/10

1. Intersection Sight DistanceCase C1Ryan MillerCE 48010/19/10

2. Objective • Introduction • Approach sight triangles • Departure sight triangles • Special situations

3. Introduction • Intersections with yield control on minor road • Considers crossing maneuver from minor road • Must consider both approach and departure sight triangles • Sight distances needed by drivers exceed those for stop-controlled approaches

4. Introduction • Minor road vehicle can cross major road without stopping if no potentially conflicting vehicles on major road • Minor road vehicle assumed to decelerate at rate of 1.5 m/s2while traveling from decision point to intersection • Minorroad vehicle assumed to cross and clear intersection at 60% of design speed

5. Approach Sight Triangles • Distance along minor street to major street (a) • Distance along major street to vehicle with right-of-way (b) • Must check both left and right directions • Use Exhibit 9-60 to find (a) • Use equations 9-2 to find (b)

6. Approach Sight Triangles

7. Approach Sight Triangles

8. Approach Sight Triangles

9. Approach Sight Triangles Vmajor= 45 mph Both approach grades= 0% Vminor= 25 mph Lw= 12 ft La=19 ft (PC)

10. Approach Sight Triangles

11. Approach Sight Triangles a= 130 fta=142 ft ta= 4.0 s tg= 6.5 s b=b= 1.47Vmajortg= 1.47x45x6.5= 430 ft

12. Approach Sight Triangles

13. Departure Sight Triangles • Departure sight triangles automatically considered • tg must meet minimum value from exhibit 9-57 (used for B3 intersection)

14. Special Cases • Major road is divided highway with narrow median • Consider additional crossing width • Major road is divided highway with wide median • Crossing maneuver need only consider crossing near lanes • Crossing far lanes must be accomplished from stopped position (departure triangle)