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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, [email protected]
• Neil Spiller, FHWA: 202-366-2188, [email protected]
• Ram Jagannathan, Leidos: 703-303-7134, [email protected]
Thanks for your participation!
Enjoy your lunch!