Congestion Identification and Bottleneck Prediction Ram Jagannathan (Leidos), Hesham Rakha (VTTI), Joe Bared (FHWA), Neil Spiller (FHWA)

VASITE 2014 Annual Meeting – VA Beach, June 26, 2014

Project Scope

Congestion Identification • Definition of Congestion

• Congestion Identification Methodology

• Classification of Congestion

• Selection of MPOs with Real-time and Archived Data

• Creating a ‘Causal Congestion Pie Chart’

• Congestion on Arterials

• Definition

• Methodology to Identify Congestion on Arterials

Project Scope (cont’d.) Bottlenecks and Solutions • Definition of Bottlenecks

• Framework for Identifying Bottlenecks

• Framework to Identify the Causes of Bottlenecks and Bottleneck Solutions

• Existing Solutions from Literature and Current Practice

• Five Specific Solutions (Dynamic Junction Control, Dynamic Lane Use at Signalized Intersections, Acceleration Lane lengths and Traffic Operations, Hard Shoulder Running between Interchanges, Reduced Lane Widths and Increased Number of Lanes)

• Analysis Methodology

• Results and Applicability Criteria

• Benefit-Cost values

• Recommendations

• Research on Innovative Solutions

• Bottlenecks Prediction

Congestion Definition

Congestion Definition (cont’d.)

• Congestion is a traffic condition where the travel speed is below a certain breakdown speed value on that facility.

• Congestion is a traffic condition where the travel speed is below a certain breakdown speed value for the prevailing roadway and weather conditions on that facility.

• Congestion is a traffic condition where the travel speed is below the free flow speed on that facility.

• Congestion is a traffic condition where the travel speed is below the free flow speed for the prevailing roadway and weather conditions on that facility.

• Congestion is a traffic condition where the travel speed is below the speed at capacity on that facility.

• Congestion is a traffic condition where the travel speed is below the speed at capacity for the prevailing roadway and weather conditions on that facility.

Bottleneck Definition

• Much of the previous research classified a “bottleneck” as any a location where there is a physical reduction in the roadway width (e.g., lane blockage); this type of bottleneck is called a “physical bottleneck.”

• Some agencies may additionally specify that “bottlenecks” are understood to have a component of “localization,” which would have to be determined by individual agencies based on regionally relevant temporal or spatial boundaries of the resulting congestion.

• Some researchers and agencies use references to “congestion” and “bottlenecks” interchangeably, making no distinction between the two terms.

• To clarify the distinction, the research team proposes that “active bottlenecks” be understood to be the term used to describe a cause and “congestion” to be the term used to describe the effect. This enables us to distinguish between cause and effect such that the proposed treatments and solutions for addressing moving and stationary bottlenecks prevent the effect (congestion), which results in delays and capacity reductions.

Bottleneck Definition (cont’d.)

• In general, active bottlenecks can be stationary or non-stationary.

• Examples of stationary bottlenecks - lane drops, merge sections, etc.

• Examples of non-stationary bottlenecks - slowly moving trucks, vehicle maneuvering aggressively, etc.

• Recommended bottleneck definitions: Bottlenecks are defined as “an area of diminished capacity that causes congestion”. Bottlenecks can be the result of physical characteristics or operational conditions on the roadway, both of which can be latent when demand is low or operational conditions change and, consequently, will not cause congestion.

• ‘Active’ operational bottlenecks can be further classified as either moving or stationary. Signal timing bottleneck - stationary bottleneck, slow moving truck - moving bottleneck.

Congestion Classification

• Facility: The type of road where the congestion occurs, such as a freeway, arterial, etc.

• Magnitude: The intensity, duration, extent and variability of the congestion.

• Intensity/Severity, Duration, Extent/Location, Variability

• Recurring vs. Non-recurring: Congestion is classified as a “recurring” if it occurs a certain number of times at the same location for certain magnitude of the problem; otherwise it is considered as a nonrecurring congestion. The number of occurrences threshold can be determined by the agencies.

• A congested condition repeated once a day for at least a month due to severe weather conditions and the range of delay was between 10 and 20 minutes per vehicle.

• Congestion repeated at least 20 days per month for roadway maintenance (work zone) where the speed reduction was between 15 percent to 20 percent.

• Recommended definition of “recurring”: Congestion that occurs more than once at the same location for a certain magnitude of the problem

Congestion Classification (cont’d.)

• Localized/Systemic definition for impact/area of influence: Congestion is classified as “localized” if its length of influence, intensity and duration is less than certain threshold (determined by the agencies); otherwise, it is considered systemic congestion. Some examples for the localized congestion thresholds could be as follows:

• A congested condition’s influence(queue) length is less than 1 mile.

• A congested condition’s delay time is less than 15 minutes per vehicle.

• The total vehicle hours of delay is less than 1,000 vehicle hours.

• A congested condition’s duration is less than 30 minutes.

• A congested condition’s influence(queue) length is less than 1 mile and the delay time is less than 5 minutes per vehicle.

Congestion Classification (cont’d.)

Bottleneck Solutions – Tailored to Challenges

Active

Bottleneck

Geometric-

Roadway

Specific

Geometric-

Facility

Specific

Geometric-

Specific to

InterchangesOperational

Challenges-

Agency Related

Operational

Challenges-

Driver Related

Operational

Challenges- Non-

motorists Related

1.Design

Speed

2. Number of

Lanes

3. Lane Width

4. Presence

and type of

shoulders

5. Lane drops

6. Lane

Reduction

Transition

7. Hz

clearance

8. Vl clearance

9. Sun Glare

Alignment

10. Hz

Alignment

11. Vl

Alignment

12. SSD

13. Pavement

friction/

surface

14. Cross

Slope

15. Super-

elevation

16. Access pts

17. Mid-block

Crossing

18. Medians

19. Lighting/

Glare

20. Marking

21. Bicycle

lanes

22. Separation

Type of

Managed

Lanes

1. Bridges

2. Tunnel and

underpass

3. Collector-

distributor

network

1. Merge/

Diverge

Sections

2. Auxiliary

Lanes

3- Weaving

Areas

4. On-ramp/Off-

Ramp

5. Acceleration/

Deceleration

lanes

Geometric-

Intersections/

TCD/ITS

1. Intersection

Sight distance

2. Left-turn

and RT lane

overflow

3. Parking

4. TCD (signal,

stop sign, etc.)

1. Managing

Demand

2. Intersection

Spacing

3. Interchange

Spacing

4 Policy on

Entry/Exit ramp

placement

5. Posted speed

limit (Static/

dynamic)

6. Signal Timing

Administration

7. Traffic

composition

8. Work zone

9- Roadway

Closure

Administration

10. Incident

management

and clearance

11. Ramp

metering

12. Heavy

vehicles

exclusion/

prohibition for

certain lanes/

routes

13. Managing

lanes

14. Response to

weather

15. Over height

management

policy

16. Congestion

Pricing

17. Toll booths

operation

18. Service

patrols

placement

19. Law

enforcement

policy/location

20. Forecasting

Traffic Demand

1. Bunching

vehicle

2. Roadside

distraction/

rubbernecking

3. Non-roadside

distractions

4- Unsafe

vehicle

condition for

weather

condition

5. Aggressive

lane change/

weaving

6. Driving

unauthorized

roadway section

7- Driver

performance in

wz

8- Driver

performance

when involved

in an incident

9- Driver

performance on

a roadway with

an incident

10. Driver

performance

with regard to

emergency

vehicle

11- Driver

performance wrt

TCD

12. Driver

performance wrt

conventional

and alternative

intersections

13. Driver

performance wrt

peds, cyclists

14. Driver

performance wrt

animal crossing

15. Driver

performance wrt

commercial and

heavy vehicle

operation

1. Sub-optimal

peds and

bicyclist

performance

(1) (2)

(3)

(4)

(5) (6) (7)

Bottleneck Solutions – Tailored to Challenges

• Lane Drops

• Description/Definition of the Element “Dropped Lane—a through lane that becomes a mandatory turn lane on a conventional roadway, or a through lane that becomes a mandatory exit lane on a freeway or expressway. The end of an acceleration lane and reductions in the number of through lanes that do not involve a mandatory turn or exit are not considered dropped lanes.”

• Theoretical/Empirical Effects: Inversely related to flow; a decrease in the number of through lanes decreases the through movement capacity on the roadway.

• Using data from a freeway lane drop in Minneapolis, it was shown that the discharge flow was about 10% lower than the prevailing flow observed prior to queue formation

• Existing Solutions

• Advance lane drop warning

• Late Merge techniques

• Dynamic Merge techniques

• Change/optimize the location of lane drops

• Avoid lane drops at low-volume exit ramps

• New Solutions

• Dynamic Lane Use Assignment using Electronic Pavement Markings

Congestion Identification

Congestion is a traffic condition where the travel speed is below the speed at capacity for the prevailing roadway and weather conditions on that facility.

Option 1:

• Agency provide the “cutoff speed” for a given location and operational conditions. Speeds below the “cutoff speed” deemed congested; else uncongested.

Option 2:

• Semi-Automated tool to identify congestion in a for agencies

• Step1: Provide cross-referenced speed, incidents, weather, workzone, roadway closure for a roadway (region)

• Step 2: Choose confidence intervals

• Step 3: Bi-Modal Distributions (congested/uncongested) for all operational conditions

• Step 4: Every spatio-temporal data point will be tagged as congested or uncongested

Bottleneck Prediction

• Tool to predict FUTURE bottleneck state for agencies

• Step1: Data Inputs include spatio-temporal congested data points with CURRENT incidents and FUTURE weather, workzone, roadway closure for a roadway (region)

• Step 2: Choose confidence intervals and FUTURE time of interest (15min, 30 min, 45 min, 60 min and 120 min)

• Every spatio-temporal data point in FUTURE will be tagged as congested/uncongested

Upcoming Products (next 6 months)

• Comprehensive Guide for Agencies – Congestion and Bottlenecks

• Tools: Congestion Identification, Bottleneck Identification, Congestion “Causal PieChart” Creator, Bottleneck Prediction

• Webinars, Workshops, Research Papers

Contacts

• Joe Bared, FHWA: 202-493-3314, joe.bared@dot.gov

• Neil Spiller, FHWA: 202-366-2188, neil.spiller@dot.gov

• Ram Jagannathan, Leidos: 703-303-7134, ram.j@leidos.com

Thanks for your participation!

Enjoy your lunch!