Lecture 6: Stop Sign Control & Signalized intersections & Design LOS

1. Lecture 6: Stop Sign Control & Signalized intersections & Design LOS Lecture objectives: By the end of this lecture the student will be able to: • Explain there is hierarchy of intersection control • Use the warrants for 2-way stop control • Evaluate traffic signal warrants (by volume only) • Apply the knowledge to the Moark Junction design

2. The Hierarchy of Intersection Control Intersection Control Options: How much judgment can drivers safely exercise to avoid collisions? Three levels of control are available. Which one will be proper for the Moark Junction in the future?

3. Level II Control: STOP Control Warrants for two-way STOP sign 16.3.1 Two-way stop control Because the STOP sign causes a substantial inconvenience to motorists, it should be used only where warranted. A STOP sign may be warranted where one or more of the following conditions exist: • Intersection of a less important road with a main road where application of the normal ROW rule would not be expected to provide reasonably safe operation. • Street entering a through highway or street. • Unsignalized intersection in a signalized area. • High speeds, restricted view, or crash records indicate a need for control by the STOP sign.

4. Level III Control: Traffic Control Signals • While warrants and other criteria for STOP and YIELD signs are somewhat general in the MUTCD, warrants for signals are quite detailed. Advantages of traffic signal control • Provide for the orderly movement of traffic • Increase the traffic-handling capacity of the intersection if applied properly and physical layout is conducive • Reduce the frequency and severity of certain types of crashes, esp. right-angle collisions • Provide for continuous or nearly continuous movement at a definite speed when coordinated (by coordination) • Used to interrupt heavy traffic at intervals to permit other traffic, vehicular or pedestrian, to cross http://mutcd.fhwa.dot.gov/HTM/2003r1/part4/part4c.htm

5. Disadvantages of traffic signal control • Excessive delay (when timing is improper) • Excessive disobedience of the signal indications (when red interval is improperly long) – may encourage red-light running • Increased use of less adequate routes as road users attempt to avoid the traffic control signal • Significant increases in the frequency of collisions (especially rear-end collisions)

6. Warrants for traffic signals Data requirements • Traffic volumes in each approach, at least 12 consecutive hours (24 hrs count preferred) containing the highest % of 24-hour traffic (include two peak periods) • 15-min counts by approach and movement classified by vehicle type during the 2 hours in the AM and PM peak periods (4 hours total) • Pedestrian counts in each crosswalk during the same 4 hours in item 2 • Information on nearby facilities and centers serving the movement disadvantaged (young, elderly, or disabled) • Posted or statutory speed limit and/or the 85the percentile speed • A condition diagram • A collision diagram • For the two peak AM and two peak PM hours: • Vehicle-hours of stopped delay for each approach • Number and distribution of gaps • Speed limits • Pedestrian delays for at least two 30 minute peak pedestrian delay periods • Queue lengths on STOP-controlled approaches

7. Warrants MUTCD 2000 has 8 warrants for a traffic signal. They are guides, not specifications. Use professional judgments. (Note MUTCD 2009 became effective January 15, 2010. Two years to comply. • Warrant 1: Eight-hour vehicular volume (1a: minimum traffic volume; 1b: interruption of traffic; 1c: combination of warrants) • Warrant 2: Four-hour vehicular volume • Warrant 3: Peak hour • Warrant 4: Pedestrian volume • Warrant 5: School crossing • Warrant 6: Coordinated signal system • Warrant 7: Crash experience • Warrant 8: Roadway network Signals

8. Signal warrant 1A: 8-hour volume Min. vehicle volume: Principal factor is the intersection traffic volume. Must satisfy for each of any 8 hour of an average day. • May reduce the values by 30% if the 85th percentile speed on the major approach is greater than 40 mph or population is less than 10,000 (built-up area of isolated community).

9. Signal warrant 1B Interruption of continuous traffic: The volume requirements must be met for each of any 8 hours of an average day. • May reduce the values by 30% if the 85th percentile speed on the major approach is greater than 40 mph or population is less than 10,000 (built-up area of isolated community).

10. Signal warrant 1C Combination of warrants: Only in exceptional cases. When none of them are satisfied but when the first two warrants of Warrant 1 are satisfied to the extent of 80% of the stipulated volumes.

11. Signal warrant 2: 4-hour volume Check for each of any 4 hr of an average day

12. Signal warrant 3: Peak-hour volume Justified where traffic condition during 1 hr of the day result in undue delay to traffic on the minor street. (factories, office park etc.)

13. Signal warrant 3B: delay This applies to cases in which STOP control is already in effect for the minor road. Cannot jump from no-contro or YIELD to signals. This warrant is satisfied when the delay during any four consecutive 15-minute periods on one of the minor-street approaches (one direction only) controlled by a STOP sign is equal to or greater than specified levels and the same minor-street approach (one direction only) volume and the total intersection entering volume are equal to or greater than the specified levels: • Delay experienced by minor approaches 4 vehicle-hours for a one-lane approach and 5 vehicle-hours for a two-lane approach. • Volume on the same minor approaches  100 vph for one moving lane of traffic, 150 vph for two moving lanes of traffic. • The total entering volume serviced during the hour equals or exceeds 800 vph entering volume for intersections with four or more approaches or 650 vph for intersections with 3 approaches.

14. Moark Junction: Does it warrant a signal in 2033 in terms of Warrant 1if the traffic growth rate you decided to use is applied to this intersection?

15. 2009 turning counts by UDOT

16. 2009 Peak Hour Turns Estimates

17. 2030 turning count estimates

18. 2030 Peak Hour Turns Estimates