CE 7670: Advanced Traffic Signal Systems Tapan K. Datta, Ph.D., P.E. Winter 2003

Probability of Failure Method If (x-1) vehicles cross the stop bar during a time equal to G – (K1 + K2) then the average minimum headway between the vehicle is given by: Avg. Min. headway = time/volume, or G – K x-1 Where K = K1 + K2 K1 = starting delay of the platoon K2 = time required for last vehicle to cross G = green plus amber time D = constant departure headway x = number of departures G = (x-1) D + K, or, G = x D + K - D

Probability of Failure Method to Calculate Cycle Length

Probability of Failure Method to Calculate Cycle Length

Assume critical lane volume = V 3600 C * X X = [ G – (K – D)] D Where: Sum of hourly critical lane volume (V) for all phases = total critical lane volume per hour V = 3600 C *  X =  G - (K-D) * D Where: C =  G  = number of phases K = lost time = K1 + K2 G = green plus amber time D = constant departure headway x = number of departures V = 3600 C * C - (K-D) D [ ] = 3600 C CD 3600 (K-D) -

Say K = K1+ K2 = 6 sec D = 2 sec 3600* 3(6-2)  V (for  = 3) = 1800 - C* 2 21600 = 1800 - C 3600* 4(6-2)  V (for  = 4) = 1800 - C* 2 28800 = 1800 - C As V approaches 1800 vph, C approaches infinity C = 3600 (K-D) 3600 – D V Based on uniform arrival

Poisson Arrival Based on random arrivals P (x+1) =   m(x+1) e-m Where: m = average arrival per cycle = V 3600/C

Signal Phasing Design Through traffic shared with right-turn traffic Solid green followed by yellow and red Left-turn traffic: Lead left-turn Protected Green left arrow followed by yellow and red Protected/Permissive Green left arrow followed by solid green Then yellow and red

Left-turn traffic: Lag left-turn Permissive/Protected Solid green followed by green left arrow Then yellow and red Split Phasing When one approach has much higher volume than the opposing approach, only one direction traffic (including left-turn) is allowed to proceed in a protected manner, and then the opposing traffic

The Texas Approach Trap Problem: Using protected-permitted and lead-lag phasing at the same time leads a vehicle to be trapped Solution: Waiting left-turner is able to see the ball indications which clear at the same time as opposing through traffic, and thus drivers do not make false assumptions

The Texas Concept Having at least two signal heads for through traffic in addition to five-section protected-permitted left-turn signal Reducing the visibility of circular indications of five-section left-turn signal so that they are readily visible by left-turners Modifying the restricted-visibility indications so that they continue to display a circular green to left-turners through the opposing left-turn movement’s lagging protected phase, and displaying the amber for the permitted left-turn only when the amber is on for opposing through traffic also

The Florida Recommendations Protected/Permissive left-turn phasing should be provided in all intersection approaches Protected only left-turn should be provided if: Double left-turn only lanes are operating Intersection geometric compels to do so Poor sight distance to opposing traffic Speed limit of opposing traffic is higher than 45mph Number of left-turn head-on crashes exceeds 6 per year

The Florida Recommendations Permissive/Protected left-turn phasing should be limited and restricted to the following situations: T-intersections where U-turns are prohibited 4-way intersections where the opposing approach has prohibited left-turns or protected only left-turn phasing 4-way intersections where the left-turn volumes from opposing approaches do not substantially differ throughout the various time periods of a normal day

The Florida Recommendations Split phasing can be effectively used when: Opposing approaches are offset to an extent that simultaneous left-turns from opposing directions would be impossible or hazardous Left-turn volumes are extremely heavy on opposing approaches and both are nearly equal to the adjacent through movement critical lane volume Left-turn volume is extremely heavy on an approach that does not include a separate left-turn lane Drivers are permitted to turn left from more than one lane and also to use right-most left-turn lane as a through lane.

The Kentucky Recommendation Protected/Permissive is the preferable method because of savings in time compared to protected only phasing Protected/Permissive should not be used if the following conditions exist: Approach speed > 45mph Protected only is currently in use and speed limit is over 35 mph Left-turn movement must cross three or more opposing through lanes Intersection geometrics force the left-turn lane to have a separate signal head Double left-turn only lanes on the approach Left-turn head-on crashes is 4 or more per year Potential left-turn problem exists documented by a traffic conflict study A sight distance problem exists

Lane Configuration for the Intersection of Gratiot Avenue and 23 Mile Road

Future AM Peak Hour Traffic Volumes for Gratiot Avenue and 23 Mile Road Approach Volume = 1,257vph 23 MILE ROAD 187+10=197 180 726 340+11=351 728+5=733 Approach Volume = 1,295vph 100 361+4= 365 Approach Volume = 651vph 498+6=504 99 298 156+5=161 47 Approach Volume = 558vph Total Intersection Volume = 3,761 vph

Phasing Plan for Gratiot and 23 Mile Road 1 2 3 4 5 6

Example 5 x 5 lane road Four phase signal timing plan 380 140 100 100 280 470 940 100 180 180 200 Critical lane volumes V1 = Max [(760+200)/2, (380+140)/2] = 480 V2 = Max [180,100] = 180 V3 = Max [(940+180)/2, (470+100)/2] = 560 V4 = Max [280,100] = 280 760

Start by assuming a cycle length Calculate ‘m’ for each phase Say 90 seconds Calculate ‘m’ for each phase V 3600/C m= m1= 480 3600/90 = 12 m2= 180 3600/90 = 4.5 m3= 560 3600/90 = 14 m4= 280 3600/90 = 7

Phase length ‘G’ for various % of failure Use Figure 7-3 to find the phase length ‘G’ for various percentages of failure  m Phase length ‘G’ for various % of failure 2 5 20 30 40 1 12 42 39 33 28 4.5 21 19 15 14 13 3 47 44 37 35 4 7 29 26 18 TOTAL CL 139 128 106 98 92

If the arrivals of cars are random Cycle length of 98 seconds has 30% of failure Cycle length of 92 seconds has 40% failure

Now assume a 100-second cycle length Calculate ‘m’ for each phase V 3600/C m= m1= 480 3600/100 = 13.3 m2= 180 3600/100 = 5.0 m3= 560 3600/100 = 15.6 m4= 280 3600/100 = 7.8

Phase length ‘G’ for various % of failure Use Figure 7-3 to find the phase length ‘G’ for various percentages of failure  m Phase length ‘G’ for various % of failure 2 5 20 30 40 1 13.3 44 41 35 33 31 5.0 23 21 17 15 14 3 15.6 51 48 37 4 7.8 29 TOTAL CL 149 139 116 106 100

If the arrivals of cars are random Cycle length of 106 seconds has 30% of failure Cycle length of 100 seconds has 40% failure

Comprehensive Example: Intersection of Rochester Road and E Comprehensive Example: Intersection of Rochester Road and E. Wattles Road, Troy Michigan

SPEED LIMIT 45 Sign N Blockbuster Video Store Papa Romano’s Pizza Ridley’s Bakery Cafe ONLY 38’ Merchant of Vino Beverage Outlet RIGHT LANE MUST TURN RIGHT Sign ONLY Kinko’s Copy Center Accent Florist 173’ ROCHESTER ROAD ONLY Comerica Bank ONLY NO TURN ON RED Sign RIGHT LANE MUST TURN RIGHT Sign NO TURN ON RED Sign 12’ 12’ 12’ 12’ 13’ 13’ SPEED LIMIT 40 Sign 9’ 6’ 24’ 65’ 138’ 22’ 41’ 3’ 12’ ONLY ONLY 19’ 14’ ONLY 12’ 11’ ONLY ONLY ONLY 13’ 17’ ONLY 12’ ONLY 43’ E. WATTLES ROAD Street Name Signs SPEED LIMIT 40 Sign NO TURN ON RED Sign 75’ 176’ 7’ 8’ 34’ 8’ RIGHT LANE MUST TURN RIGHT Sign NO TURN ON RED Sign ONLY Pavement markings very faded 108’ Shell Gasoline Station ONLY TO I-75 Sign Wendy’s Restaurant 20’ SPEED LIMIT 45 Sign 13’ 13’ 11’ 13’ 14’ Condition Diagram for Rochester Road and E. Wattles Road - Troy, Michigan

WESTBOUND E. WATTLES ROAD EASTBOUND E. WATTLES ROAD NORTHBOUND ROCHESTER ROAD SOUTHBOUND ROCHESTER ROAD

AM Peak 8-9 AM 73 678 109 103 616 150 76 258 70 567 191 N PM Peak 5-6 PM 467 554 116 103 1135 300 241 568 90 331 130 Midday Peak Noon- 1 PM 56 497 98 91 855 204 155 225 141 76 242 162 Traffic Volumes for Rochester Road and East Wattles Road - Troy, Michigan

Phasing Diagram for Existing Condition N-S Through/Right Phase 3 4 N-S Left-Turn Phase E-W Left-Turn Phase 2 1 E-W Through/Right Phase

Capacity Analysis For Existing Traffic Conditions CYCLE APPROACH INTERSECTION INTERSECTION LENGTH LOS LOS DELAY (SEC) (SEC/VEH) Northbound E 100 Southbound D E 48.8 Eastbound F Westbound C Northbound E 90 Southbound D E 48.3 Eastbound F Westbound C Northbound E 80 Southbound D E 48.4 Eastbound F Westbound C

Crash Data TYPE OFCRASH YEAR AVERAGE NUMBER OF CRASH 1997 1998 CRASHES PER YEAR Rear-End 46 33 39.5 Angle Intersection 1 2 1.5 Angle Driveway 26 33 29.5 Left-Turn Head-On Inter. 2 3 2.5 Left-Turn Head-On Dway. 2 4 3 Sideswipe 7 6 6.5 Other 3 1 2 INJURIES 15 12 13.5 TOTAL PER YEAR 87 82 84.5

LEGEND FOR COLLISION DIAGRAMS Collision Diagrams for 1997 and 1998 LEGEND FOR COLLISION DIAGRAMS Rear-End Backed Into Head On Angle Left-Turn Head-On Sideswipe Fixed Object Parked Vehicle Pedestrian Other Injury Fatality *

Collision Diagram for Rochester Road and E. Wattles Road for 1997 10/6 4/16 6/28 1/19 9/20 6/20 12/30 12/8 11/12 6/17 2/28 8/29 7/14 12/22 N Rochester Road 5/23 11/18 3/14 1/17 4/7 7/1 4/23 7/19 10/19 12/2 2/28 5/2 12/20 E. Wattles Road 9/4 1/29 7/8 5/5 2/24 5/15 9/10 5/5 6/3 3/28 7/14 3/29 * 8/24 2/14 4/16 4/7 6/25 6/6 4/12 7/28 5/24 5/17 10/16 1/8 12/19 10/11 1/16 3/9 7/29 10/22 6/10 2/12 5/27 11/1 7/15 5/30 12/9 1/29 9/12 1/30 5/21 9/8 8/15 11/11 8/20 12/30 6/23 4/21 3/15 4/9 5/25 10/16 4/3 3/6 8/2 9/18 9/3 10/29 7/1 8/13 10/23 4/29 Collision Diagram for Rochester Road and E. Wattles Road for 1997

Collision Diagram for Rochester Road and E. Wattles Road for 1998 11/20 11/20 4/22 10/17 6/30 6/24 9/15 1/19 6/30 N Rochester Road 11/9 6/9 1/4 1/30 10/1 2/17 3/27 12/23 3/10 2/27 E. Wattles Road 11/20 3/20 10/8 10/30 9/20 10/2 8/3 9/2 3/19 6/22 6/30 2/23 9/26 6/29 1/17 6/20 9/30 3/3 1/7 6/25 12/10 6/11 5/11 7/9 12/21 7/7 6/11 4/14 5/13 8/10 8/9 7/22 3/29 6/1 5/22 7/17 5/27 11/9 3/27 1/7 7/29 1/2 7/10 3/17 10/3 7/15 4/10 8/30 12/9 6/1 2/11 7/30 12/29 2/14 3/6 10/15 7/15 4/30 8/17 9/29 12/20 10/9 11/26 Collision Diagram for Rochester Road and E. Wattles Road for 1998

Phasing Diagram for Modified Signal Timing Signal Timing Modifications to Existing Traffic Conditions Include right turn phase with exclusive left turn phase for: Southbound approach Eastbound approach Westbound approach Phasing Diagram for Modified Signal Timing E-W Left-Turn and SB Right Turn Phase 2 4 N-S Left-Turn and E-W Right Turn Phase E-W Through/Right Phase 1 N-S Through/Right Phase 3

Capacity Analysis For Existing Traffic Conditions with Signal Timing Modifications CYCLE APPROACH APPROACH INTERSECTION INTERSECTION LENGTH LOS LOS DELAY (SEC) (SEC/VEH) Northbound E 100 Southbound D E 47.1 Eastbound F Westbound C Northbound E 90 Southbound D E 44.6 Eastbound F Westbound C Northbound E 80 Southbound D E 46.9 Eastbound F Westbound C

Cycle length using Webster’s Equation Existing Condition y1 = (568 + 90)/ (1800 * 2) = 0.188 or = (331 + 116)/ (1800 * 2) = 0.124 y2 = 241/1000 = 0.241 or = 130/1000 = 0.130 y3 = (1135 + 300)/(1800 * 2) = 0.40 or = (554 + 467)/(1800 * 3) = 0.189 y4 = 103/1000 = 0.103 or = 116/1000 = 0.116 Y = 0.188 + 0.241 + 0.40 + 0.116 = 0.945 C = 1.5 * (2 * 4) + 5 / ( 1-0.945) = 309 second cycle length

Calculate Splits 1 split = 0.188 * 90/ 0.945 = 18 sec Assume Cycle Length = 90 seconds Split = Green interval + Yellow interval + All-red interval 1 split = 0.188 * 90/ 0.945 = 18 sec 2 split = 0.241 * 90/ 0.945 = 23 sec 3 split = 0.40 * 90/ 0.945 = 38 sec 4 split = 0.116 * 90/ 0.945 = 11 sec

Calculate Clearance Interval CI = t + v 2(a ± Gg) w + L + Speed Limit on Rochester Road = 45 mph = 66 fps t = 1 sec, a = 10 ft/sec/sec CINS = 1 + 66/(2 * 10) + (110 + 20)/ 66 = 4.3 sec + 2.0 sec = 6.3 seconds Speed Limit on E. Wattles Road = 40 mph = 58.67 fps CIEW = 1 + 58.67/(2 * 10) + (116 + 20)/ 58.67 = 3.9 sec + 2.3 sec = 6.2 seconds

Signal Timing Plan 1 2 3 4 E-W Through/Right Phase 1 Left-Turn Phase 2 N-S 3 4 G = 12 sec G =18 sec G = 32 sec G = 6 sec A = 4 sec A = 3 sec A = 4 sec A = 3 sec R = 74 sec R = 69 sec R = 54 sec R = 81 sec AR = 2 sec AR = 2 sec AR = 2 sec AR = 2 sec

Proposed Improvements High right turn volume for Northbound Rochester Road Include exclusive right turn lane using existing pavement width

SPEED LIMIT 45 Sign Papa Romano’s Pizza Ridley’s Bakery Cafe Blockbuster Video Store N ONLY 38’ Merchant of Vino Beverage Outlet RIGHT LANE MUST TURN RIGHT Sign ONLY Kinko’s Copy Center Accent Florist 173’ ONLY ROCHESTER ROAD Comerica Bank ONLY NO TURN ON RED Sign RIGHT LANE MUST TURN RIGHT Sign NO TURN ON RED Sign 11’ 11’ 11’ 11’ 15’ 15’ SPEED LIMIT 40 Sign 9’ 6’ 24’ 65’ 138’ 22’ 41’ 3’ 11’ ONLY ONLY 11’ 11’ 11’ 10’ 11’ ONLY ONLY ONLY ONLY 12’ 11’ ONLY ONLY 11’ 11’ E. WATTLES ROAD 43’ Street Name Signs SPEED LIMIT 40 Sign NO TURN ON RED Sign 75’ 176’ 7’ 8’ 34’ 8’ RIGHT LANE MUST TURN RIGHT Sign NO TURN ON RED Sign ONLY ONLY 108’ Shell Gasoline Station RIGHT LANE MUST TURN RIGHT Sign TO I-75 Sign ONLY ONLY Wendy’s Restaurant 20’ SPEED LIMIT 45 Sign 12’ 11’ 10’ 10’ 11’ 10’ Proposed Intersection Diagram for Rochester Road and E. Wattles Road - Troy, Michigan

Phasing Diagram for Proposed Improvements with Laneage Modification 4 N-S Left-Turn and E-W Right Turn Phase E-W Through/Right Phase 1 N-S Through/Right Phase 3 2 E-W Left-Turn and N-S Right Turn Phase

With Proposed Improvements- Laneage Modifications Capacity Analysis With Proposed Improvements- Laneage Modifications CYCLE LENGTH (SEC) APPROACH LOS INTERSECTION DELAY (SEC/VEH) Northbound D Southbound C Eastbound E 100 Westbound 32.9 90 38.0 80 39.4

Traffic Signal Warrants

Engineering studies should be performed Traffic signals should not be installed unless one or more of the warrants are met Engineering studies should be performed and compared with warrants analysis should consider effects of right turn volumes proportion subtracted from volumes should be based on engineering judgement

Warrants for Signalized Intersections Warrant 1: Minimum Vehicular Volume

satisfied when the volumes given in the table exits on major street and on the higher volume minor street for any 8 hours of an average day when 85th percentile speed of major street exceeds 40 mph 70 % of the requirements may be used

Warrant 2: Interruption of Continuous Traffic Warrant Applies where traffic volume on major street is so high that traffic on minor intersecting street experiences excessive delay.

satisfied when, the volumes given in the table exists on the major street on the higher-volume minor street the signal installation will not seriously disrupt progressive traffic flow for each of any 8 hours of an average day when 85th percentile speed of major street exceeds 40 mph 70 % of the requirements may be used

Warrant 3: Minimum Pedestrian Volume Warranted where the pedestrian volume crossing the major intersection or mid-block location during an average day is: 100 or more for each of any four hours, or 190 or more in any one hour The pedestrian volume of the major street may be reduced as much as 50% of the values given above when predominant pedestrian crossing speed is below 3.5 fps

Warrant 4: School Crossing warranted at an established school crossing when a traffic engineering study of the frequency and adequacy of gaps in a traffic stream shows that the number of adequate gaps in the traffic stream during the period when the children are using the crossing is less than the number of minutes in the same period. T = 3 + + F width of street 4 Where F = Number of children per group - 1 (2) 5 ( ) A minimum of 50 children should be utilizing the crossing before applying this warrant

Warrant 5: Progressive Movement Warranted in order to maintain proper grouping of vehicles and effectively regulate group speed The warrant is satisfied when: on a one-way street or a street which has predominantly unidirectional traffic on a two-way street adjacent signals do not provide the necessary degree of platooning and speed control,and the proposed and adjacent signals could constitute a progressive signal system Should be based on the 85% speed unless study indicate other speed is more desirable

Warrant 6: Accident Experience This warrant is satisfied when: Adequate trial of less restrictive remedies with satisfactory observance and enforcement has failed to reduce the accident frequency; and Five or more reported accidents, of types susceptible to correction by traffic signal control, have occurred within a 12-month period,and There exists a volume of vehicular and pedestrian traffic not less than 80 percent of the requirements specified in the warrants Any signal installation will not seriously disrupt progressive traffic now.

Warrant 7: Systems Warrant A major route has one or more of the following characteristics: It is part of the street or highway system that serves as the principal network for through traffic flow; It includes rural or suburban highways outside of, entering, or traversing a city; It appears as a major route on an official plan, such as a major street in a transportation study

Warrant 8: Combination of Warrants Signals may be justified where no single warrant is satisfied but where Warrants 1 and 2 are satisfied to the extent of 80 percent or more of the stated values

Warrant 9: Four Hour Volumes Satisfied when, each of any four hours of an average day the plotted points representing the vehicles per hour on the major street (total of both approaches) and the corresponding vehicle per hour on the higher volume minor street approach (one direction only) all fall above the curve in Figure 4-3 for the existing combination of approach lanes

85 percentile speed exceeds 40 mph, the four hour volume requirement is satisfied when the plotted points referred to fall above the curve in figure 4-4 for the existing combination of approaches.

Warrant 10: Peak Hour Delay Satisfied when these conditions exist for one hour of an average weekday Total delay experienced by traffic on a side street controlled by STOP sign equals or exceeds four vehicle-hours for a one-lane approach and five vehicle-hours for a two-lane approach, and The volume on the side street approach equals or exceeds 100 vph for one moving lane of traffic or 150 vph for two moving lanes, and The total entering volume services during the hour equals or exceeds 800 vph for intersection with four (or more) approaches or 650 for intersections with three approaches

Warrant 11: Peak Hour Volume Satisfied when, the plotted point representing the vph the major street (total of both approaches) and the corresponding vehicles per hour of the higher volume minor street approach (one direction only) for one hour of an average day falls above the curve in Figure 4-5 for the existing combination of approach lanes When the 85th percentile speed exceeds 40mph, peak hour volume requirement is satisfied when the plotted point falls above the curve in figure 4-6 for the existing combination of approach lanes

Example: Main Road with existing driveway 12-hour traffic counts Major Street is Dequindre Road (N-S) Has 2 NB lanes and 2 SB lanes Speed limit = 45 mph 85th percentile speed = 47 mph Minor Street is Beaumont Hospital driveway approach One right turn lane and one left turn lane

Beaumont Hospital and the proposed signal location at the driveway On Dequindre Road South of driveway

12-hour Traffic Volumes

Warrant #1 Requirements (for 8 hours): Can use the 70% reduction, since 85th percentile speed > 40 mph Major Street (total of both approaches) with 2 or more lanes 600* 0.70 = 420 vph Minor Street (one approach) with 2 or more lanes 200 * 0.70 = 140 vph

Warrant No. 1 is not met

Warrant #2 Requirements (for 8 hours): Can use the 70% reduction, since 85th percentile speed > 40 mph Major Street (total of both approaches) with 2 or more lanes 900* 0.70 = 630 vph Minor Street (one approach) with 2 or more lanes 100 * 0.70 = 70 vph

Warrant No. 2 is met

Warrant # 9 Requirement (4 hours) Use Figure 4-4 since 85th percentile speed exceeds 40 mph lower threshold volume for a minor street approach with two or more lanes is 80 vph, when the traffic volumes on the major street exceed 875 vph.

Warrant No. 9 is met

Warrant # 11 Requirement (one hour): Use Figure 4-6 since 85th percentile speed of the major street exceeds 40 mph lower threshold volume for a major street approach with two lanes is 100 vph when the major street volume is greater than 1200 vph.

Warrant No. 11 is met

Example: Existing Road with Proposed Driveway Proposed developments may want a traffic signal installed at a driveway location Traffic impact analysis using ITE “Trip Generation” manual Provides rates to predict number of trips generated by development Provides rates only for peak hours On this basis, only Warrant No. 11 (Peak Hour Volumes) is applicable

However, for Shopping Center Developments ITE published hourly percentages (12 hours) for variation in traffic throughout: Typical weekday Typical weekend days The rates can be used to predict traffic for a twelve hour period Can perform a warrant study based on other warrants, instead of only Warrant No. 11

For example: Number of trips predicted exiting the driveway approach during the PM peak hour (5-6 PM) = 214 vph Table 1 shows that from 5-6 PM The % of exiting traffic = 11% Use this proportion, along with the percent exiting trips for the remaining hours of the day To calculate the predicted # of exiting trips for the rest of the day

The percent of exiting trips at 10-11 AM is 6.5% Average weekday < 100,000 sq. ft. of GLA Thus, the predicted # of exiting trips (x10-11) will be 214 11 Thus, X10-11 = 126 vph 6.5 = X10-11

Similarly, for the remaining hours: 214 11 Thus, X11-12 = 163 vph 8.4 = X11-12 214 11 Thus, X12-1 = 160 vph 8.2 = X12-1 214 11 Thus, X1-2 = 146 vph 7.5 = X1-2 And so on. Results shown in following table

9:00- 10:00 PM 1.8 35

Now, perform a warrant analysis 12-hour traffic counts on major road and predicted 12-hour volumes for driveway approach Major Street is M-29 Road (E-W) Has 1EB lane and 1 WB lane with proposed center lane for left turns Speed limit = 45 mph Minor Street is proposed retail center driveway approach Two lanes

Proposed signal location for commercial development , across from existing driveway Existing driveway and M-29

12-hour traffic volumes (Existing volumes on major street and predicted volumes on minor street)

Warrant #1 is met

Warrant #2 is met

Warrant #9 is met

Warrant # 11is not met Volumes on the major street do not meet requirements

Left-Turn Phasing Warrants at Signalized Intersections Warrants based on accidents 3-5 left-turn crashes/year Correctable LTHO crashes/year ≥ 4 LTHO crashes/ 2 years ≥ 6

NUMBER OF OPPOSING LANES Left-Turn Phasing Warrants at Signalized Intersections (ITE Journal April 1986) Warrants based on volumes product of left turn and opposing volume 2 lane exceeds 30,000-50,0000 4 lane exceeds 50,000-100,000 NUMBER OF OPPOSING LANES PRODUCT 1 ≥ 45,000 2 ≥ 90,000 3 ≥ 135,000

NUMBER OF OPPOSING LANES Warrants based on volumes sum of left turn and opposing volume NUMBER OF OPPOSING LANES PRODUCT 1 ≥ 500 2 ≥ 900 3 ≥ 1000

Example Product Rule: 180 * 590 = 106,200 For 2 opposing lanes, yes the left-turn phase is warranted (≥ 90,000) 180 vph 590 vph Sum Rule: 180 + 590 = 770 For 2 opposing lanes, the left-turn phase is not warranted (< 900)

minimum left-turn hourly volumes- minimum left-turn volume per cycle exceeds 125 vph minimum left-turn volume per cycle exceeds 2 vehicles/cycle

Delay Analysis Maximum Allowable delay = 96 sec/veh OR minimum total delay = 1.5 vehicle-hours

Other warrants geometric design- sight distance inadequate signal system- progressive movement/adjacent intersection phasing traffic conflict- exceeds 10-14/hour approach speed- of opposing traffic exceeds 45 mph