Yang Lu Xianfeng Yang Xiaoli Sun May Progress report on Median U-Turn (MUT) planning model

Summary of previous work Literature view Federal UAID Report Team workers’ previous work on CFI. Other related papers/reports/websites on MUT Team discussion Analysis the unique characteristics of MUT Further clear out tasks

Median U-Turn Median U-Turn (MUT) Also called “Michigan Left ”. Left turns at the intersection are not allowed. Instead, to turn left, drivers must drive straight or turn right, then make a U-turn at a median crossover, guided by sign like the one at right. Michigan Lefts have been part of Michigan roadways since at least the late 1960s. Red Line - divided highway traffic turning left onto crossroad. Green Line - crossroad traffic turning left onto divided highway. Source: “The Michigan Left” website

Median U-Turn Full MUT No left-turn movements were allowed from the minor road at the main intersection. Partial MUT Left-turn movements were allowed from only the minor road at the main intersection.

Literature review Federal UIAD report AdvantagesDisadvantages Lower overall travel time Increased capacity at the main intersection Better progression on the major street Enhanced safety Pedestrians may enjoy some benefits with this design Access management may be enhanced Higher right-of-way and construction costs Difficulties meeting driver expectations.

Literature review Federal UIAD report Typically, MUT intersection increases throughput for 30%-45%. Total network travel time savings usually out-weighted the additional travel time of U-turns. Typically, total crash reduction ranges from 20%-50%. Head-on and angle crashes were significantly reduced at MUT intersections.

Literature review Bared and Kaisar (2002) studied the operational benefits of signalized MUT for left-turn vehicles making indirection maneuvers. They found that although the average travel time for the MUT traffic is higher than direct left turn (DLT), the overall reduction in the network travel time of MUT is significant for balanced flows. Similar benefits are derived from a reduction in the percent of stops. Authors also discussed geometric features as acceleration lane on the cross road, left-turn lanes, offset for the median U-turn, etc. MUTs require equal travel time as the DLTs at low to medium volumes and less travel time at higher traffic volumes. Yang and Zhou (2004) evaluated the operational performances of DLT and MUT through simulation in terms of the delay and travel time under different traffic volumes. The authors found that with an increase in the through-traffic volume on the major road, the delay as well as the travel time of DLT were higher than those of MUT.

Literature review Univ. of South Florida did a comprehensive research on MUT intersections. (Liu et al (2007, 2007(2), 2008, 2008(2)) The authors analyzed the operational effects of MUTs vs. DLTs. Making MUT at a signalized intersection has comparable total travel time as compared with DLT; The percentage of drivers selecting MUT increases with the upstream through traffic volume, left- turn volume from major road into the driveway, and the total left-turn traffic demand. The authors estimated the capacity of MUT intersections. Developed a model to estimated critical gap for U-turns; Developed a model to estimate the follow-up time for U-turns; Developed a model to estimated the capacity of U-turn movements with above two model; Found that the median width is a significant impact factor. As to traffic safety, they found MUT generally safer than DLT. The authors also addressed the following issues at unsignalized MUT intersections: Estimation of the conflicting traffic volumes for U-turn movements, Evaluation of the impedance effect of minor street right-turn movement on the capacity of U-turns, and Evaluation of the effects of U-turns on the capacity of the major street exclusive left-turn lane. Found that the capacity of the exclusive left-turn lane decreases with an increase in the major street traffic volume, the major street right-turn volume, and the percentage of U-turning vehicles at the exclusive left-turn lane.

Summary of literature Compared with conventional DLT movement MUT improves traffic safety MUT has higher capacity MUT reduces delay/travel time under heavy traffic demand Federal UIAD report provided various untraditional intersection assessment methodology to help the project planning and decision-making. Geometric features were discussed in one paper. However, no quantity guidelines provided on geometric features, such as turning-bay length, median width, etc. Traffic operation were evaluated, but no quantity guidelines on traffic signal optimization.

Tasks Max queue length model Previous queue model 1 (signal-exist case) and queue model 2 (merge case) can be adopted in MUT planning model. Develop additional queue models If the crossover is un-signalized, vehicles from the crossover need to seek gaps to cross all through lanes to arrive to the right-turn bay. The distance between the crossover and the right-turn bay as well as the number of through lanes also affect the “gap seeking” behavior. Short distance will make gap seeking difficult. More number of through lanes makes gap seeking difficult. Queue model 1 and 2 do not cover this case.

MUT(Signalized) Critical Points

MTU ( Unsignalized) Critical Points

MUT(Signalized) Queue Models NumberReasonDemandQueue Model 1signalEBT & WBL NA 2signalEBTQueue model 1 3signalWBT & EBL NA 4signalWBTQueue model 1 5signalWBLQueue model 1 6signalEBLQueue model 1 7signalNBT,NBRQueue model 1 8signalSBT,NBRQueue model 1 *NA indicates that we need to establish an appropriate queue model for the segment

MUT(Unsignalized) Queue Models NumberReasonDemandQueue Model 1signalEBT & WBL NA 2signalEBTNA 3signalEBLNA 4signalWBLNA 5signalNBTQueue model 1 6signalSBTQueue model 1 *NA indicates that we need to establish an appropriate queue model for the segment

References Bared, J. G. and Kaisar, E. I. (2002). “Median U-turn design as an alternative treatment for left turns at signalized intersections,” Institute of Transportation Engineers. ITE Journal. Hughes, W., Jagannathan, R., Sengupta, D., and Hummer, J. (2010). “Alternative Intersections/Interchanges: Informational Report (AIIR),” Publication No. FHWA-HRT , U.S. Department of Transportation, Federal Highway Administration Office of Safety, Washington, DC. Liu, P., Lu, J. J., and Cao, B. (2008). “Estimating Capacity of U-Turns at Unsignalized Intersections: Conflicting Traffic Volume, Impedance Effects, and Left-Turn Lane Capacity,” Transportation Research Record, No. 2071, Transportation Research Board of the National Academies, Washington, D.C., pp. 44–51. Liu, P., Lu, J. J., Fatih, P., Dissanayake, S., and Sokolow, G. (2007). “Should Direct Left- turns from Driveways be replaced by Right-turns followed by U-turns? The Safety and Operational Comparison in Florida,” Submitted to the 3rd Urban Street Symposium. Liu, P., Lu, J. J., Hu, F., and Sokolow, G. (2008). “Capacity of U-Turn Movement at Median Openings on Multilane Highways,” Journal of Transportation Engineering, Volume 134, Issue 4, pp Liu, P., Lu, J. J., Zhou, H. G., and Sokolow, G. (2007). “Operational Effects of U-Turns as Alternatives to Direct Left-Turns,” Journal of Transportation Engineering, Vol. 133, No. 5, May 2007, pp Lu, J. J. and Liu, P. (2005). “Operational Evaluation of Right Turns Followed by U-turns at Signalized Intersection (4-lane arterials) as an Alternative to Direct Left Turns,” Florida Department of Transportation, Tallahassee, FL.

References Rodegerdts, L. A., Nevers, B., Robinson, B., Ringert, j., Koonce, p., Bansen, J., Nguyen, T., McGill, J., Stewart, D., Suggett, J., Neuman, T., Antonucci, N., Hardy, K., Courage, K. (2004). “Signalized Intersections: Informational Guide,” Report No. FHWA-HRT , Federal Highway Administration. “The Michigan Left” Yang, X. K. and Zhou, H. G. (2004). “CORSIM-Based Simulation Approach to Evaluation of Direct Left Turn versus Right Turn Plus U-Turn from Driveways,” Journal of Transportation Engineering, Vol. 130, No. 1, pp

Xianfeng Yang May Progress report on DDI planning model

Introduction of DDI DDI (Double crossover diamond interchange) interchange differs in the way that the left and through movements navigate between the ramp terminals. The purpose of this interchange design is to accommodate left-turning movements onto arterials and limited-access highways while eliminating the need for a left- turn bay and signal phase at the signalized ramp terminals.

Signal Design

Queue model Selection LocationDescriptionQueue model selection 1，21，2 Queue cause by two different demands New Model required 3，43，4 Merging problemQueue Model 2 5，65，6 Signalized QueueQueue Model 1 7，87，8 Signalized QueueQueue Model 1