Progress report on Median U-Turn (MUT) planning model
Yang LuXianfeng YangXiaoli SunMay 28 2010Progress report
onMedian U-Turn (MUT) planning modelSummary of previous
workLiterature view Federal UAID ReportTeam workers previous work
on CFI.Other related papers/reports/websites on MUTTeam
discussionAnalysis the unique characteristics of MUTFurther clear
out tasks
Median U-TurnMedian 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 websiteMedian U-TurnFull MUTNo
left-turn movements were allowed from the minor road at the main
intersection.Partial MUTLeft-turn movements were allowed from only
the minor road at the main intersection. Literature reviewFederal
UIAD reportAdvantagesDisadvantagesLower overall travel
timeIncreased capacity at the main intersectionBetter progression
on the major streetEnhanced safetyPedestrians may enjoy some
benefits with this designAccess management may be enhancedHigher
right-of-way and construction costs Difficulties meeting driver
expectations.
Literature reviewFederal UIAD reportTypically, 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 reviewBared 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 reviewUniv. 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, andEvaluation 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 literatureCompared with
conventional DLT movementMUT improves traffic safety MUT has higher
capacityMUT reduces delay/travel time under heavy traffic
demandFederal 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. TasksMax queue length modelPrevious queue
model 1 (signal-exist case) and queue model 2 (merge case) can be
adopted in MUT planning model.Develop additional queue modelsIf 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 Model1signal EBT &
WBLNA2signalEBTQueue model 13signalWBT & EBLNA4signal WBTQueue
model 15signalWBLQueue model 16signalEBLQueue model
17signalNBT,NBRQueue model 18signalSBT,NBRQueue model 1*NA
indicates that we need to establish an appropriate queue model for
the segmentMUT(Unsignalized) Queue Models
NumberReasonDemandQueue Model1signal EBT &
WBLNA2signalEBTNA3signalEBLNA4signal WBLNA5signalNBTQueue model
16signalSBTQueue model 1*NA indicates that we need to establish an
appropriate queue model for the segment14ReferencesBared, 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-09-060, 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. 4451.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. 147-154.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.
327-334.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.ReferencesRodegerdts,
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-04-091,
Federal Highway Administration.The Michigan Left
http://www.michiganhighways.org/indepth/michigan_left.htmlYang, 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. 68-75Xianfeng YangMay 28 2010Progress report onDDI planning
modelIntroduction of DDIDDI (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 SelectionLocation
DescriptionQueue model selection12Queue cause by two different
demandsNew Model required34Merging problemQueue Model 256Signalized
QueueQueue Model 178Signalized QueueQueue Model 1
