Right-Turn Traffic Volume Reduction in Traffic Signal Warrant Analysis: A Delay Perspective

Research Project for Nevada Department of Transportation Right-Turn Traffic Volume Reduction in Traffic Signal Warrant Analysis: A Delay Perspective Presenter: Cui Zhou University of Nevada, Reno Center for Advanced Transportation Education and Research March 27, 2014

Presentation Overview • Introduction • Previous Research • ITE Community Discussion • Problems in Existing Methods • Proposed Methodology • Case Study • Summary and Conclusions

Introduction • Importance of Traffic Signal Warrants • What’s traffic signal warrants? Standard: An engineering study of traffic conditions, pedestrian characteristics, and physical characteristics of the location shall be performed to determine whether installation of a traffic control signal is justified at a particular location.

Introduction • Importance of Traffic Signal Warrants • What’s traffic signal warrants? Standard: An engineering study of traffic conditions, pedestrian characteristics, and physical characteristics of the location shall be performed to determine whether installation of a traffic control signal is justified at a particular location. • Consequences of an unwarranted signal • Rear-end collisions • Excessive delay and congestion • Disobedience of signals

Introduction • Importance of Traffic Signal Warrants • What’s traffic signal warrants? Standard: An engineering study of traffic conditions, pedestrian characteristics, and physical characteristics of the location shall be performed to determine whether installation of a traffic control signal is justified at a particular location. • Consequences of an unwarranted signal • Rear-end collisions • Excessive delay and congestion • Disobedience of signals • In short, traffic signals should be only installed when they will alleviate more problems than they induce.

Introduction • Right-turn Traffic in Traffic Signal Warrants

Introduction • Right-turn Traffic in Traffic Signal Warrants • MUTCD and MTSD have clearly stated that some portion of the right-turn traffic should be reduced from the minor street traffic count.

Previous Research Right-turn adjustments are usually based on engineering judgment (EJ), field observation (FO), or an accepted right-turn adjustment methodology (AM).

ITE Community Discussion Our topic was posted in the ITE community discussion section in October 2013and eight responses were received in this survey

Problems In Existing Methods • Most of them are based on engineering judgments

Problem In Existing Methods • Most of them are based on engineering judgments • Pagones Theorem and NCHRP methods are relatively sound

Problem In Existing Methods • Most of them are based on engineering judgments • Pagones Theorem and NCHRP method are relatively sound • The intersection’s LOS after reduction is often one alphabet better • Pagones Theorem fails to take into account the uneven volume distribution • The NCHRP method works out the reduction based on the conflicting major-road. It doesn’t give any thought to the through and left turn traffic

Methodology • The approach is based on delay equivalence • Find the delay equivalent relationship between right-turn and through traffic

Methodology • The approach is based on delay equivalence • Find the delay equivalent relationship between right-turn and through traffic • The estimation of control delay is implemented in VBA programming in EXCEL according to HCM 2010

Methodology • An isolated intersection is studied Directional ratio= WB Volume: EB Volume

Methodology • An isolated intersection is studied • Five minor-street lane conditions are discussed

Condition 1 • Different traffic volume scenarios are applied (12,096 cases in total)

Condition 1 • Different traffic volume scenarios are applied (12,096 cases in total) One Study Situation 20% LT

Condition 1 • Different traffic volumes scenarios are applied (12,096 cases in total) • The reduction factor could be calculated:

Condition 1 The reduction factor graph in one specific study situation where the mainline volume is 500 vph with 1:1 directional ratio

Condition 1 The reduction factor graph in one specific study situation where the mainline volumes are 500 vph with 1:1 directional ratio

Condition 1 • Reduction Factor Table

Condition 2 • Using the same traffic volume scenarios, almost the same reduction factors are obtained • From here, we could also see that the assumed left-turn percentage doesn’t significantly affect the equivalent results

Condition 3 • 20 left turns and zero through traffic are assumed before reduction. The right-turn movement volume is from 50 vph to 510 vph with 20 vphincrement • The adjusted minor street volume is the maximum of adjusted right-turn and through & left-turn traffic ( critical volume)

Condition 4 • Minor street left-turn and through volume is from 40 vph to 700 vph with 20 vph increment • Reduction factor graph when the mainline volume is 500 vph.

Condition 5 • Because there is exclusive left-turn lane, left-turn traffic is not considered in this condition. • Reduction Factor Table

Case Study • 26 intersections’ turning volumes provided by NDOT • According to 8 hour warrant in MUTCD, divide these cases into three categories: • warrant meets without right turning (7 cases); • warrant doesn’t meet with all turning movement (12 cases); • warrant meets when considering all turning movement (7 cases)

Case Study: Lamoille Hwy and Spring Creek Pkwy Lamoille Hwy Spring Creek Pkwy

Case Study: Lamoille Hwy and Spring Creek Pkwy

Case Study: US395 and Airport Rd US395 Airport Rd

Case Study: Lamoille Hwy and Spring Creek Pkwy

Summary and Conclusions • Unwarranted traffic signals are detrimental

Summary and Conclusions • Unwarranted traffic signals are detrimental • Engineers agree on reducing right-turn volumes, but there is no mature guidance

Summary and Conclusions • Unwarranted traffic signals are detrimental • Engineers agree on reducing right-turn volumes, but there is no mature guidance • This paper proposed a new guideline which is based on the equivalent relation when rightturnsand through traffic achieve the same delay

Summary and Conclusions • Unwarranted traffic signals are detrimental • Engineers agree on reducing right-turn volumes, but there is no mature guidance • This paper proposed a new guideline which is based on the equivalent relation when right turns and through traffic achieve the same delay • Five conditions are divided, and further 63 study situations are providedin each condition

Summary and Conclusions • Unwarranted traffic signals are detrimental • Engineers agree on reducing right-turn volumes, but there is no mature guidance • This paper proposed a new guideline which is based on the equivalent relation when rightturnsand through traffic achieve the same delay • Five conditions are divided, and further 63 study situations are providedin each condition • Case studies were conducted. The proposed guideline can easily help engineers make sound decisions for the adjustment of right turns

Thank you for listening! Suggestions and Questions?

Right-Turn Traffic Volume Reduction in Traffic Signal Warrant Analysis: A Delay Perspective