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

Explain there is hierarchy of intersection controlUse the warrants for 2-way stop controlEvaluate traffic signal warrants (by volume only)Apply the knowledge to the Moark Junction design

Lecture objectives: By the end of this lecture the student will be able to:

The Hierarchy of Intersection ControlIntersection 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?

Level I Passive control – basic rules of the road apply No control Guide signs only Warning sings with or without guide signs

Level II Direct assignment of ROW to major street or rotational ROW YIELD control (roundabouts are in this category) Two-way STOP control All-way STOP control

Level III

Positive alternate assignment of exclusive ROW Traffic signals: 2-phase, multiphase Traffic control agent/officer

Warrants for two-way STOP sign

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:

A. 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.

B. Street entering a through highway or street.

C. Unsignalized intersection in a signalized area.

D. High speeds, restricted view, or crash records indicate a need for control by the STOP sign.

Level II Control: STOP Control16.3.1 Two-way stop control

Level III Control: Traffic Control SignalsWhile 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

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)

Data requirements1. 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)

2. 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)

3. Pedestrian counts in each crosswalk during the same 4 hours in item 2

4. Information on nearby facilities and centers serving the movement disadvantaged (young, elderly, or disabled)

5. Posted or statutory speed limit and/or the 85the percentile speed

6. A condition diagram

7. A collision diagram

8. For the two peak AM and two peak PM hours:

a) Vehicle-hours of stopped delay for each approach

b) Number and distribution of gaps

c) Speed limits

d) Pedestrian delays for at least two 30 minute peak pedestrian delay periods

e) Queue lengths on STOP-controlled approaches

Warrants for traffic signals

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

Warrants

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).

Signal warrant 1BInterruption 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).

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.

Signal warrant 2: 4-hour volume

Check for each of any 4 hr of an average day

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.)

Signal warrant 3B: delay

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:

1. Delay experienced by minor approaches 4 vehicle-hours for a one-lane approach and 5 vehicle-hours for a two-lane approach.

2. Volume on the same minor approaches 100 vph for one moving lane of traffic, 150 vph for two moving lanes of traffic.

3. 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.

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.

Moark Junction: Does it warrant a signal

in 2035 in terms of Warrant 1

if the traffic growth rate you decided to use is applied to this intersection?

2009 turning counts by UDOT

2009 Turning Count Data

Hour Begin US 6 EB LT US 6 EB TH US 6 EB Total US 6 WB TH US 6 WB RT US 6 WB Total US 89 SB RT US89 SB LT US 89 SB Total Hourly Entering Vehicles

0:00 4 64 68 59.0 5 64 4 2 6 138

1:00 6 46 52 49.0 4 53 1 0 1 106

2:00 0 51 51 39.0 0 39 1 0 1 91

3:00 6 43 49 31.0 2 33 1 0 1 83

4:00 3 51 54 40.0 1 41 2 2 4 99

5:00 0 143 143 66.0 9 75 12 15 27 245

6:00 0 350 350 138.0 18 156 12 17 29 535

7:00 0 414 414 149.0 27 176 16 27 43 633

8:00 10 501 511 197.0 35 232 32 29 61 804

9:00 19 487 506 280.0 30 310 24 40 64 880

10:00 23 471 494 269.0 31 300 31 26 57 851

11:00 23 458 481 212.0 32 244 40 24 64 789

12:00 20 460 480 191.0 29 220 33 29 62 762

13:00 16 428 444 224.0 35 259 38 29 67 770

14:00 20 463 483 206.0 67 273 40 28 68 824

15:00 17 445 462 244.0 86 330 53 38 91 883

16:00 15 451 466 209.0 75 284 38 41 79 829

17:00 23 403 426 208.0 45 253 47 39 86 765

18:00 14 390 404 226.0 49 275 45 25 70 749

19:00 14 317 331 186.0 32 218 38 18 56 605

20:00 16 244 260 195.0 24 219 33 17 50 529

21:00 21 195 216 157.0 24 181 21 10 31 428

22:00 15 145 160 124.0 18 142 12 5 17 319

23:00 12 95 107 99.0 13 112 8 5 13 232

Total 297 7115 7412 3798 691 4489 583 466 1049 12950

US89 Northbound at Moark Junction = 297 + 691 = 988

2009 Peak Hour Turns Estimates

SB Right

SB total

2035 turning count estimates

2035 Turning Count Data Growth factor = 1.05 (0.2% annual, 26 years for 2035)Hour Begin US 6 EB LT US 6 EB TH US 6 EB Total US 6 WB TH US 6 WB RT US 6 WB Total US 89 SB RT US89 SB LT US 89 SB Total Hourly Entering Vehicles

0:00 4 67 72 62 5 67 5 2 7 1461:00 6 48 55 52 4 56 1 0 1 1122:00 0 54 54 41 0 41 1 0 1 963:00 6 45 52 33 2 35 1 0 1 874:00 3 54 57 42 1 43 2 2 5 1055:00 0 151 151 70 9 79 12 16 28 2586:00 0 369 369 145 19 164 13 18 31 5647:00 0 436 436 157 28 185 17 28 45 6678:00 11 528 538 208 37 244 34 31 64 8479:00 20 513 533 295 32 327 25 42 67 927

10:00 24 496 520 283 33 316 33 27 60 89711:00 24 482 507 223 34 257 42 25 67 83112:00 21 485 506 201 31 232 34 31 65 80213:00 17 451 468 236 37 273 39 31 70 81114:00 21 488 509 217 71 288 42 29 72 86815:00 18 469 487 257 91 348 56 40 96 93016:00 16 475 491 220 79 299 40 43 83 87317:00 24 424 449 219 47 266 50 41 91 80618:00 15 411 426 238 52 290 48 26 74 78919:00 15 334 349 196 34 230 40 19 59 63820:00 17 257 274 205 25 231 35 18 53 55821:00 22 205 228 165 25 191 22 11 33 45122:00 16 153 169 131 19 150 13 5 18 33623:00 13 100 113 104 14 118 9 5 14 245

Total 313 7494 7807 4001 728 4728 614 491 1105 13640max hourly vol 538 max hourly vol 348 max hourly vol 96 930

US89 Northbound at Moark Junction = 313+728 = 1,041

2035 Peak Hour Turns Estimates

56 4091

2035 Peak hour volumes estimates

18257

469