Coordinated Operations, notes from the field

Edward FokResource Center Operations Technical Service Team

2005 TRB Annual Meeting

What’s all the hubbub?

• Improved driver experiences• Reduced emission from fewer stops• Improved safety from predictable operation• Better transit operation from improved roadway

reliability

So Why can’t we coordinate everything?

Coordination

• Chicken or the Egg• What came first? The driver or the engineer?

• More Cycle Length then you can shake a stick at!• Network Coordination or snowflakes? Which is

more delicate?• Field checks are never an option

• Famous last words: "Field check? What's that?"• Measure Quantify and Test…we ARE the

government!

Chicken or the Egg (or who came first? The driver or the engineer?)

Driver? Demand based Coordination

• Observe existing platoon arrival patterns• Adjust offset to Capture platoon to arrive on start

of green• Provide sufficient lead in to allow queue to clear

before new platoon arrives

Washington D.C.

Engineered? Designed Coordination

• Coordination are considered at the planning stage

• Cycle length and Offset are predetermined.• Drive at the rated speed or expect to have stops• “Deviation are not permitted"

• Yes, there ARE network progression!!!

Los Angeles, CA

The Story Does not end there

• Cycle length had to increase to meet new demands

• Designed Coordination eventually became Demand Based Coordination

• Network of signals became network of intersecting arterials.

Chicken or the Egg? It doesn’t matter, it’s all Omelets at the end of the meal.

Before you start throwing Eggs at me…

• Posted Speed Limit vs Designed Speed• Posted Speed Limit

• Simplify customer calls• Helps to protect against litigations if correctly set.

Coordination and the Need for Speed

Be aware of wide green band when using coordination for speed control!

More Cycle Length then you can shake a stick at!• How big of a difference?• What are the causes?

• Temporary surges in Sources or Sinks?• Freeway off-ramp or on-ramp?

• Fully actuated signal needs cycle length too!• Data Data Data!!!

Unless there are drastic changes supported by observation in the field, keep the cycle length the same!!!

Coordination and Events

• Engineered coordination are critical• Special events planning• Coordination between temporary channelization and

signal timing – Focus on facilitating the temporary Origin-Destination pathways.

• Traffic Officers – Critical link to inattentive drivers

Your Traffic is in My Signals

• Match Cycle Length• Share volume and timing information• Pick up the PHONE!!!

~3 miles

Free Operation inside a Coordinated Network?

Free Operations (Fully Actuated Control) in a Coordinate Network

-Use of both Max Green and Volume Density Control

Available storage capacity are critical to success

2980 feet

1730 feet

2690 feet

2650 feet

2110 feet1820 feet

2640 feet

Network Coordination or snowflakes:Which is more delicate?

• Death by School Zones (Especially when Law Enforcement are present)

• Death by Emergency Preemption• Death by Railroad Crossings• Death by Loading Zones

Interruption are generally temporary,Recovery time needed is highly dependent on existingLevel of saturation.

Death by Parking

Extended violation causes massive disruption

• Changes in channelization

•Flow ‘turbulence’

•Reduction in safety

Death by Pedestrians

Problem from consistent flow of Pedestrian Traffic

•Seasonal variation

•Planned event driven

•Special Needs Operation

•Sabbatical Ped Recall!!

•Over 55 Intersection

•Forced recall operation.

Death by Shopping-Reseda (It's really Los Angeles, but don't tell them that)

114 Yds

125 Yds176 Yds

Field Checks Are Never An Option!

• Verify New Timing• Did the technician put in the correct offset?• Did someone check the controller clock?

• Validate New Timing• Woa! What’s this a new sewer line going in? • Are they driving where we though they were

driving???

Hollywood, CA (It's still Los Angeles, but they could be in denial)

What the original Coordination assumption Correct?

So what did we actually do?

• Justify your existence – before and after performance evaluation!

• Which Measure of Effectiveness does your customer care about?• Volume?• Delay?• Travel Time?• Number of Stop?• Speed?

• Best Tool for Evaluation: Floating Car Studies

The Truth about Time-Space Diagram

Tim

e

Distance

Actual Platoon Speed Profile

Late Arrivals Speeds up

Lead vehicle acceleration

from stop

So Is it the Chicken or the Egg?

• Understand the nature of the coordination problem: Is it due to urban layout or due to driver/capacity problems?

• Coordination cannot be guaranteed at all times.• Computer optimization is only the beginning, not the end to

coordination.• Get ready to get your hands dirty!