DETERMINATION OF INTERSECTION CONTROL TYPE USING THE HCM

1. DETERMINATION OF INTERSECTION CONTROL TYPE USING THE HCM SAMUEL KOFI AHIAMADI Graduate Student University of Nevada, Reno Email: skahiamadi@yahoo.com ZONG TIAN (PhD, PE) University of Nevada, Reno Email: zongt@unr.edu

2. Outline • Introduction • Objective • Methodology • Results • Conclusions • Recommendations

3. Background • Before the 1990, TWSC, AWSC and Signals were the preferred intersection controls • After being introduced into the U.S. in 1990, roundabouts have become very popular with over 2000 in use • Appropriate intersection control selection is critical for operational efficiency and safety • Marek et al produced an intersection selection chart for TWSC, AWSC and signals

4. Background Cont’d • Since roundabouts are used in over 40 states in the US this research was to follow the earlier effort but include roundabouts since • they are safer than other at-grade intersections • and operate more efficiently with minimal delay and queue • Low maintenance cost

5. Objective • The primary objective of this research was to develop guidelines (presented in a chart) for the preliminary determination of the best intersection control option given traffic volumes and geometric information.

6. Methodology • Developed generic intersections for comparing the analysis from chapters 18-21 and 33 of the HCM 2010 • Adopted procedure from Marek et al and modified to include parameters for roundabouts. (Figures a, b, c, d).

7. TOOLS USED • aaSIDRA and SYNCHRO software • HCM 2000 • HCM 2010 • MUTCD 2009

8. Table 1. Intersection Volume Split

9. Characteristics of Generic TWSC and AWSC Intersection

10. Characteristics of Generic Signal and Roundabout Intersection

11. Results for LOS

12. Results for Average Control Delay

13. Results for Average Queue

14. Results for Single-Lane Intersection

15. Results for Double-Lane Intersection

16. Conclusions • Roundabouts can accommodate a wide range of traffic volume conditions with better performance than other intersection control types. • Given the traffic volume conditions at an intersection, the charts developed can be used to determine the optimal intersection type based on selected performance measures (control delay, queue or LOS).

17. Conclusions Cont’d • Average intersection control delay and average intersection queue length appeared to be better performance indicators for selecting intersection control types compared to LOS. • Roundabouts showed superior performance over a wide range of traffic volume combinations compared to other intersection control types although signalized intersections are still a better options when the traffic volumes are high

18. QUESTIONS?THANK YOU