Isolated Timing Operations - Workshop on Best Practices for Signal Timing

Isolated Timing Operations -Workshop on Best Practices for Signal Timing • Bill Kloos • Signals & St. Lighting Division Manager • City of Portland, Oregon City of Portland - Isolated Timing Operations

A typical day in Portland! City of Portland - Isolated Timing Operations

Mt. St. Helens is at it again! City of Portland - Isolated Timing Operations

Traditional Approach • Why have the presence detection and still have the sign? • How does this relate to detection in the street? • Or, the real question is: • What’s Peter’s thing about the toilet??? City of Portland - Isolated Timing Operations

Talk outline for today • Goals for isolated intersection operation • Review of recent ITE report on the signal timing practices - “State of the Practice” • When should we display the Yellow? • Review of Portland left turn operation • Closing issues and questions City of Portland - Isolated Timing Operations

Goals for isolated intersection operation • Safety • Not require panic stops • Not have veh/peds in unsafe situations • Display yellow at “best” time • Efficiency • Minimum delay • Minimum stops City of Portland - Isolated Timing Operations

Goals for isolated intersection operation • Bill’s basics: • Keep the cycle length as short as possible • Provide “snappy” operation, especially for minor movements • Provide for “safe” display of yellow • Don’t violate KISS principle City of Portland - Isolated Timing Operations

Signal Timing Practices and Procedures - State of the Practice ITE - March 2005 Phil Tarnoff and Javier Ordonez City of Portland - Isolated Timing Operations

Report based in part on a survey • 100 state, city, and county agencies responded • Included questions in following categories - • Controller types • General considerations for timing (phasing, etc) • Timing for actuated controllers • Timing plan selection and calculation processes • Traffic responsive and adaptive systems • Retiming of individual intersections and systems City of Portland - Isolated Timing Operations

State of the Practice findings • Phasing - • phasing selection practices - little agreement • Left-turn phasing - more permissive than anticipated • Signal timing at isolated intersections • wide variance on calculating max, min, and ext City of Portland - Isolated Timing Operations

State of the Practice findings City of Portland - Isolated Timing Operations

State of the Practice conclusions • “After 50 years there is still disagreement and lack of understanding on many of the fundamental aspects of traffic signal timing.” • There is “inconsistency in the engineering processes being used, as well as a surprising degree of reliance on the judgement of the engineer or technician responsible for the timing process.” • “A definitive document defining best practices is needed.” City of Portland - Isolated Timing Operations

Recent ITE Listserv discussion “Using yellow as green” • What is the probability of someone stopping at certain time distance from stop bar? • More opinion than fact. • Main question - at what point will someone continue through the intersection at the onset of yellow? City of Portland - Isolated Timing Operations

Issues and questions • When should we display the yellow to the approaching motorist? • Portland method displays the yellow when motorist is at stop bar • Some research suggests that most motorists will not stop when yellow is displayed less than 2 seconds in advance of stop bar • For efficiency, shouldn’t we display the yellow that much sooner? • Note on this question - somebody else try first City of Portland - Isolated Timing Operations

City of Portland basics • Use Type 170 controllers • Wapiti IKS actuated controller software • Primarily use ILD (round loops) • Basic detection timing functions used: • Min green • Passage • Volume density (TBR, TTR, Min gap, added/actuation) City of Portland - Isolated Timing Operations

Typical data sheet City of Portland - Isolated Timing Operations

Detection Timing - City of Portland (cont) • Multiple input channels per phase • Allows carryover/delay programming within CPU • Can have 3 sets of timing parameters (time transfer) • Have separate table for entering carryover and delay by channel • Can do various “tricks” with Command Box City of Portland - Isolated Timing Operations

Advance detection vs stop bar • Use method discussed by Peter K for advance detection • For side streets and left turns, use two-double loops from stop bar and one single detector at 100’ from stop bar. • Most side streets set in “non-locking” operation City of Portland - Isolated Timing Operations

Left Turn Example - SW Barbur & Hamilton Major Street City of Portland - Isolated Timing Operations

City of Portland - Isolated Timing Operations

36’ Timing • Min = 3 sec • Ext = 0.5 sec • Yellow = 3.0 sec • Carryover back loop = 2.1 sec 100’ Left Turn Example - SW Barbur & Hamilton City of Portland - Isolated Timing Operations

Opposing traffic indication LT lane City of Portland - Isolated Timing Operations

How should it work? City of Portland - Isolated Timing Operations

Desired operation - the video pause City of Portland - Isolated Timing Operations

Single vehicle operation Min time overrides gap City of Portland - Isolated Timing Operations

Left turn signal now yellow Left turn signal now red Max time out issues City of Portland - Isolated Timing Operations

Issues and questions • We already have a reasonable body of knowledge on how to make isolated intersections work better. Why aren’t we using it? • Current fully actuated theory does not work any better (usually worse) under congested than pretimed. How do we handle the boundary between free flow operation and congestion? • How do we truly get to a “best” practice? City of Portland - Isolated Timing Operations

Finally - Is there a silver bullet for improving local intersection operations? No, but maybe by using old techniques and new technology we can come up with some silver buckshot that will make things better! City of Portland - Isolated Timing Operations

The End

Isolated Timing Operations - Workshop on Best Practices for Signal Timing