Pedestrian Timing Strategies at Large Signalized Intersections...PD = Ped Detector HLD = Phase Hold...

Transportation Research GroupUniversity of Nevada, Reno

2009 TRB Pedestrian Workshop

Pedestrian Timing Strategies at Large Signalized Intersections

Zong Tian, Ph.D., P.E.Department of Civil & Environmental Engineering

University of Nevada RenoReno, NV 89557

OVERVIEW

Safety – Efficiency Issue• Impact of pedestrian timing on signal operations

Pedestrian Timing Strategies• Two-stage crossing• Split phasing• Exclusive ped phase

Summary and Conclusions

PED. CROSSING AT TRAFFIC SIGNALS

Pedestrian crossing concurrent with parallel vehicle movementSufficient time must be provided to allow pedsafely crossing

Green >= WALK + FDWConflict with turning vehicles

SAFETY VS. EFFICIENCY

Safety EfficiencyLong WALK + FDW Long Green (Minor St.)

Less Green (Main St.)Ped. Protected Phase Increased Lost Time

(Separate Ped and Vehicles) Less Capacity

Safety Efficiency

2008 Nevada Fall Transportation Conference

LARGE INTERSECTIONS

Minor St.

ISSUES

Low vehicle demand but long ped timeTwo-stage crossing = longer ped delaySignificant impact under split phasingCoordination issue (ped time treatments)

TWO-STAGE PEDESTRIAN CROSSING

PEDESTRIAN TIMING SCENARIOS

“Pedestrian Delay Models at Signalized Intersections Considering Signal Phasing and Pedestrian Treatment Alternatives” (09-2537) by Wang et al.

• One-stage crossing• Current two-stage without overlaps• Two-stage with overlaps

SPLIT PHASING

Sequentially providing green and serving the two opposite approaches

PED. TREATMENT UNDER SPLIT PHASING

Left-turn green arrow(Protected LT)

No left-turn arrow(Permitted LT)

Dynamic display(Protected/Permitted)Acknowledgement: Some of the following pictures were borrowed from a presentation by Scott Wainwright of FHWA

T im e

** Two Pedestrian Splits

PROTECTED LEFT TURN

SB Vehicles Need 30” Green per Cycle

NB Vehicles Need 15” Green

Peds Need 5” Walk + 30” FDW

Total Vehicle Need = 45”Total Ped Need = 70”

T im e

** One Pedestrian Split

PERMITTED LEFT TURN

a) W ith C onflicting Pedestrian C rossings on B oth Sides

b) W ith C onflicting Pedestrian C rossings on East Side

PROTECTED/PERMITTED LEFT TURN

c) W ith C o n flict in g P ed estria n C r os sing s o n W est Sid e

d) W ith o ut C o n flict ing Ped estria n C ro ssin g s

Φ7 Φ9*

Φ1 Φ2

Φ5 Φ6

Φ3Φ10*

Φ8 (Ped Left)

Φ4 (Ped Right)

Ring 1

Ring 2

Ring 3

Ring 4

* Note: It may require to output φ9 and φ10 load switches to φ8 and φ4, respectively

e) Controller Phase and Ring Structures

Back Panel Wiring

Ph.8 N X T

Ph.8 O N

Ph.8 C H K

Ph.8 PO

Ph.8 O M T

Ph.8 H LD

Ph.8 PD

Ph.8 V D

Ph.7 N X T

Ph.7 O N

Ph.7 C H K

Ph.7 PO

Ph.7 O M T

Ph.7 H LD

Ph.7 PD

Ph.7 V D

Ph.4 N X T

Ph.4 O N

Ph.4 C H K

Ph.4 PO

Ph.4 O M T

Ph.4 H LD

Ph.4 PD

Ph.4 V D

Ph.3 N X T

Ph.3 O N

Ph.3 C H K

Ph.3 PO

Ph.3 O M T

Ph.3 H LD

Ph.3 PD

Ph.3 V D

D iode device

LE G EN D

V D = V ehicle D etectorPD = Ped D etectorH LD = Phase H oldO M T = Phase O m itPO = Ped O m itC H K = C heck C allsN X T = N ext PhaseO N =Phase O n

NO PED ON WEST LAG CROSSWALK(NB GREEN ARROW)

NB Approach

WITH WEST LAG PED (NB GREEN BALL)

NB Approach

STATIC OR DYNAMIC SIGN

LAS VEGAS PROTECTED/PERMITTED

* Reduced Pedestrian Splits

TWO-STAGE CROSSING

EXCLUSIVE/SCRAMBLE

Tian, Z., Urbanik, T., Engelbrecht, R., and Balke, K. Pedestrian Timing Alternatives and Impacts on Coordinated Signal Systems Under Split Phasing Operations; Transportation Research Record 1748, pp. 46-54, 2001.

0 100 200 300 400

Pedestrian Volume, ped/hr

γ =0.2

γ =0.5

γ =1.0

γ =1.5

γ =2.0

Model Elements:• Ped Volume• Cycle Length• γ = (Ta + Tb)/tp• Ped Time (tp)

Data for the Figure:• Cycle = 100 sec• tp = 35 sec

EXCLUSIVE VS. PROTECTED LT MODEL

COORDINATED SIGNALS

Two timing alternatives to handle pedestrians• Ped timing accommodation

• Longer cycle• No ped timing accommodation

• Out of synch/Transition

Tian et al. (2000) . “Pedestrian Timing Treatment on Coordinated Signal Systems”, Proceedings of ICTTS’2000, ASCE, Beijing, China.

SUMMARY AND CONCLUSIONS

Efficiency SafetyTwo-stage crossing strategiesSplit phasing Exclusive/scramble phase Coordinated signals (to be continued…)

Tian’s website at UNR:

http://unr.edu/homepage/zongt

Pedestrian Timing Strategies at Large Signalized Intersections...PD = Ped Detector HLD = Phase Hold...

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