Improving the left-turn flow at McKellips and Scottsdale Rds. IEE 545 Discrete Event Simulation December 6, 2011 Yousef Dashti Kevin O'Connor Serhan S. Alshammari Min Choi

Problem & Objective Problem –waiting time for left-turn cars on N. Scottsdale road is unreasonably high Objective—to compare two policies (current and proposed) and choose a better one o Current: Left turn at green arrow o Proposed: Left turn at green light with caution

Data Collection Data collected 5pm on a work day (rush hour) over a 15min period South bound: o 242 straight: 86.1% o 39 left : 13.9% o Mean inter arrival time was seconds North bound: o 338 straight : 93.9% o 24 left: 6.1% o Mean inter arrival time was seconds

Low Rate Data Data collected 11pm Collected actual IAT of 149 cars over 26 min period North bound: o Mean inter arrival time was seconds

H 0 : data fits an exponential distribution with mean of H 1 :data does not fit an exponential distribution with mean of Input Modeling— Equal size bins

Input Modeling— Equal prob bins

BinFrequencyEi(Oi-Ei)^2/Ei More Xo^ Input Modeling— Equal prob bins

BinFrequencyEi(Oi-Ei)^2/Ei More Xo^ Input Modeling— Equal prob bins

We failed to reject the null hypotheses that our data fits an exponential distribution with mean of Input Modeling Conclusion

Model Basics Entity: cars Attribute: arrival time Activities: crossing the intersection (straight & turn) Resources: sections of roads that must be cleared to cross the intersection (straight & turn)

Overview-Current System South Bound Cars Traffic Light Pattern

Model - Current System 1 lane for turning left 3 lanes for going straight (equal probability)

Model - Current System The left-turn lane (South bound) One of the three lanes going straight (South bound) 0.139

Model Validation The observed average waiting time of North bound cars turning left was in our sample The confidence interval of average waiting time of north bound left-turn cars generated by our model: NLW_C

Proposed Model Keeping track of the cars going straight and turning left using global variables

Proposed Model The left-turn lane (North bound) One of the three lanes going straight (South bound)

Proposed Model Freeing the resource for left-turn cars

Output Analysis Pared t-test for average waiting time for cars going North and turning left NLW_CNLW_P2d_n

Output Analysis Pared t-test for average waiting time for cars going South and turning left SLW_CSLW_P2d_s

Conclusion Our simulation analysis shows that the proposed solution (removing the left-turn arrow) significantly reduce the average waiting time of the cars turning left (both North and South bounds)

Questions ?