OPTIMIZING RAMP OPTIMIZING RAMP METERING STRATEGIESMETERING STRATEGIES

Presented byPresented by – – Kouros Mohammadian, Ph.D.Kouros Mohammadian, Ph.D.Saurav Chakrabarti.Saurav Chakrabarti.

ITS Midwest Annual MeetingITS Midwest Annual MeetingChicago, IllinoisChicago, IllinoisFebruary 7, 2006February 7, 2006

BackgroundBackground► Ramp control is the application of control devices Ramp control is the application of control devices

like ramp signals to regulate the number of like ramp signals to regulate the number of vehicles entering the mainline from feeder arterial vehicles entering the mainline from feeder arterial networks through on-ramps.networks through on-ramps.

► This restrictive measure is to achieve operational This restrictive measure is to achieve operational efficiency and optimum freeway operation in terms efficiency and optimum freeway operation in terms of of

Mainline travel time, travel speed and travel delay.Mainline travel time, travel speed and travel delay. Enhancing traffic safety.Enhancing traffic safety.

► The study focuses on comparing multiple ramp The study focuses on comparing multiple ramp

metering control measures and how each fares in metering control measures and how each fares in providing the most efficient mainline and ramp providing the most efficient mainline and ramp flow by:flow by:

1.1. Maintaining capacity flow and preventing formation of Maintaining capacity flow and preventing formation of bottlenecks on the mainline.bottlenecks on the mainline.

2.2. Preventing excessive queue formation on on-ramps andPreventing excessive queue formation on on-ramps and3.3. Preventing spillback into feeder arterial network. Preventing spillback into feeder arterial network.

Study ObjectiveStudy Objective

► Ramp control measures which have been Ramp control measures which have been researched in this study are:researched in this study are:

1.1. Base Condition of No Ramp Meter (Open Ramp)Base Condition of No Ramp Meter (Open Ramp)

2.2. Fixed Time Meter – 4 sec Cycle with 1.5 sec Fixed Time Meter – 4 sec Cycle with 1.5 sec GreenGreen

3.3. Coordinated ALINEA AlgorithmCoordinated ALINEA Algorithm

4.4. ZONE AlgorithmZONE Algorithm

► Objective is to determine the most efficient Objective is to determine the most efficient ramp control method in terms of mainline ramp control method in terms of mainline travel time, travel speed and travel delay travel time, travel speed and travel delay with respect to the study area along Dan with respect to the study area along Dan Ryan Expressway. Ryan Expressway.

Ramp Metering Control Ramp Metering Control Methods Methods

Ramp Metering

Algorithms

Isolated Coordinated

ALINEA

Local Metering

using Neural Networks

Coordinated ALINEA

ZONECOOPERATIV

ECOMPETITIVE

HELPER Algorithm

LINKED Algorithm

INTEGRATED

BOTTLENECK Algorithm

SWARM Algorithm

FUZZY LOGIC Algorithm

METALINE Algorithm

FHWA/BALL Space

Algorithm

DYNAMIC Metering Control

ALINEA Algorithm ALINEA Algorithm ► Local traffic responsive algorithm in which Local traffic responsive algorithm in which

the control logic is based on the feedback the control logic is based on the feedback structure from the mainline loop detectors.structure from the mainline loop detectors.

► The feedback control logic dynamically The feedback control logic dynamically maintains the mainline occupancy level maintains the mainline occupancy level below the target occupancy level by below the target occupancy level by restricting the inflow from on-ramps.restricting the inflow from on-ramps.

► Easy to calibrate and implement in field.Easy to calibrate and implement in field.

► Queue override feature can be incorporated Queue override feature can be incorporated in the algorithm if required.in the algorithm if required.

ALINEA AlgorithmALINEA Algorithm…(contd)…(contd)

r(t) = r(t-1) + Kr(t) = r(t-1) + KRR*(O*(Odesireddesired – O – Odownstreamdownstream(t))(t))

r(t)r(t) Metering rate at timer interval ‘Metering rate at timer interval ‘t’t’ (veh/hr)(veh/hr)

OOdesireddesiredDesired occupancy rate of the Desired occupancy rate of the downstream detector station (%)downstream detector station (%)

OOdownstreamdownstream((

t)t)Measured occupancy rate at the Measured occupancy rate at the downstream detector station (%).downstream detector station (%).

r(t-1)r(t-1) Measured on-ramp volume for time Measured on-ramp volume for time interval t-1 (veh/hr).interval t-1 (veh/hr).

KKRRRegulator parameter (veh/hr), typically Regulator parameter (veh/hr), typically set at 70 veh/hr.set at 70 veh/hr.

Zone AlgorithmZone Algorithm► First implemented by Minnesota Department of First implemented by Minnesota Department of

Transportation ( MnDOT) in the St. Pauls area of Transportation ( MnDOT) in the St. Pauls area of Minneapolis.Minneapolis.

► A type of coordinated algorithm which is based on A type of coordinated algorithm which is based on the control logic of equating the input into a zone to the control logic of equating the input into a zone to the output from the zone and thus operate the the output from the zone and thus operate the mainline at capacity.mainline at capacity.

► Pseudo code of the ZONE algorithm:Pseudo code of the ZONE algorithm:

Divide the corridor into multiple zones based on location of Divide the corridor into multiple zones based on location of critical bottlenecks in the corridor - u/s end of the zone is a critical bottlenecks in the corridor - u/s end of the zone is a free flow and the d/s is the critical bottleneck.free flow and the d/s is the critical bottleneck.

Regulate the inflow from the on-ramps so as to smooth out Regulate the inflow from the on-ramps so as to smooth out the congestion and then allow the traffic on the mainline to the congestion and then allow the traffic on the mainline to move at capacity.move at capacity.

Zone AlgorithmZone Algorithm…(contd)…(contd)

A + U + M + F = X + B + SA + U + M + F = X + B + S

AA upstream mainline volume – upstream mainline volume – measured valuemeasured value

UUsum of the volumes from non-sum of the volumes from non-metered entrance ramps in the metered entrance ramps in the defined zone - measured valuesdefined zone - measured values

MMsum of the volumes from the metered sum of the volumes from the metered entrance ramps in the defined zone - entrance ramps in the defined zone - to be calculated by the algorithmto be calculated by the algorithm

FF sum of the measured freeway to sum of the measured freeway to freeway volumes - to be calculatedfreeway volumes - to be calculated

XXis the sum of the exit ramp volumes – is the sum of the exit ramp volumes –

measured valuemeasured value

BB downstream bottleneck capacity - downstream bottleneck capacity - calibrated valuecalibrated value

SSspace available in the ZONE – space available in the ZONE – assumed to be zero for capacity assumed to be zero for capacity performanceperformance

Micro-simulation - Types of Micro-simulation - Types of MModels odels

► Macroscopic Models:Macroscopic Models:

Takes into account a more system wide Takes into account a more system wide representation of traffic flow and characteristicsrepresentation of traffic flow and characteristics

► Mesoscopic Models:Mesoscopic Models:

Platoons or groups of vehicles are taken as an Platoons or groups of vehicles are taken as an unit of analysis without any consideration of the unit of analysis without any consideration of the inter-vehicle interaction.inter-vehicle interaction.

► Microscopic Models:Microscopic Models:

Individual vehicle characteristics can be Individual vehicle characteristics can be calibrated and the inter-vehicle interactions can calibrated and the inter-vehicle interactions can be studied.be studied.

Simulation Platform – VISSIM Simulation Platform – VISSIM 4.14.1

► Microscopic traffic simulator that has been used to Microscopic traffic simulator that has been used to analyze the effect of the ramp metering algorithms analyze the effect of the ramp metering algorithms as applied to the study bed.as applied to the study bed.

► Microscopic simulators like VISSIM provide the Microscopic simulators like VISSIM provide the following features like:following features like:

Mechanical and other characteristics like speed, Mechanical and other characteristics like speed, acceleration rates etc. can be calibrated for each of the acceleration rates etc. can be calibrated for each of the vehicles, thus providing an accurate simulation of the real vehicles, thus providing an accurate simulation of the real world.world.

Inter-vehicle interaction in terms of following distance, Inter-vehicle interaction in terms of following distance, headway and driver characteristics like aggressive or headway and driver characteristics like aggressive or passive driving behavior can also be calibrated.passive driving behavior can also be calibrated.

► Simulation models and related studies are useful Simulation models and related studies are useful for cost effective impact studies like in this case.for cost effective impact studies like in this case.

VISSIM 4.1VISSIM 4.1…(contd)…(contd)

► Network Elements Calibrated in Study:Network Elements Calibrated in Study:

Mainline Loop Detectors:Mainline Loop Detectors: Location of the mainline loop detectors was Location of the mainline loop detectors was critical for achieving proper control.critical for achieving proper control.

Signal Control:Signal Control: To implement the ramp control logic, the ramp signal To implement the ramp control logic, the ramp signal heads were calibrated to simulate the following conditions:heads were calibrated to simulate the following conditions:

► No Ramp of Open RampNo Ramp of Open Ramp

► Fixed-time Control with a Cycle of 4 sec and a green time of 1.5 secFixed-time Control with a Cycle of 4 sec and a green time of 1.5 sec

► Adaptive Isolated and Coordinated Algorithms using Vehicle Actuated Adaptive Isolated and Coordinated Algorithms using Vehicle Actuated Programming (VAP) which is a programmable interface for implementation of Programming (VAP) which is a programmable interface for implementation of adaptive control algorithms like:adaptive control algorithms like:

1.1. ALINEAALINEA2.2. ZONEZONE

Travel Time Measuring Zones:Travel Time Measuring Zones: Travel Time Zones were calibrated for Travel Time Zones were calibrated for collecting the mainline travel time and travel delay.collecting the mainline travel time and travel delay.

Data Collection Points:Data Collection Points: The data collection points are defined to The data collection points are defined to collect counts of vehicles crossing the section and other related data. collect counts of vehicles crossing the section and other related data.

Study Area – Dan Ryan Study Area – Dan Ryan ExpresswayExpressway

► 1.85 miles along the NB 1.85 miles along the NB Local lanes of the Dan Local lanes of the Dan Ryan Expressway from Ryan Expressway from the 63the 63rdrd street on-ramp to street on-ramp to the 51the 51stst street on-ramp as street on-ramp as shown.shown.

► 4 on-ramps in the corridor 4 on-ramps in the corridor – 63– 63rdrd, 59, 59thth, 55, 55thth and 51 and 51stst streets.streets.

► 3 off-ramps in the corridor 3 off-ramps in the corridor – 63– 63rdrd, 59, 59thth and 55 and 55thth street street

► Transfer Lanes from local Transfer Lanes from local to express lanes near 63to express lanes near 63rdrd street merge.street merge.

► Transfer Lanes from Transfer Lanes from express to local near 51express to local near 51stst street merge.street merge.

STUDYAREA

Calibration of Network Calibration of Network ParametersParameters

► Throughput target volume is based on IDOT’s Traffic Systems Center Throughput target volume is based on IDOT’s Traffic Systems Center (TSC) data.(TSC) data.

► Target occupancy rate (ALINEA) and bottleneck capacities are based Target occupancy rate (ALINEA) and bottleneck capacities are based on floating car studies and field data collection.on floating car studies and field data collection.

► Study ElementsStudy Elements

Uncontrollable Elements:Uncontrollable Elements: Uncontrollable elements involved in the study Uncontrollable elements involved in the study included:included:

► geometry of the study area.geometry of the study area.► input traffic volumes and traffic routing.input traffic volumes and traffic routing.► signal timings and traffic composition in the corridor.signal timings and traffic composition in the corridor.

Controllable Elements: Controllable Elements: Controllable elements of the network which were Controllable elements of the network which were changed to simulate the real field situation in the study included:changed to simulate the real field situation in the study included:

► Lane change parameters regarding the location where traffic starts changing Lane change parameters regarding the location where traffic starts changing lanes.lanes.

► Car following behavior and driver perceptive reaction to reflect aggressive Car following behavior and driver perceptive reaction to reflect aggressive Chicago driving behavior.Chicago driving behavior.

► Simulation resolution – number of times per simulation second a vehicle’s Simulation resolution – number of times per simulation second a vehicle’s position is calculatedposition is calculated

Simulation & TestingSimulation & Testing► Approaches: Two separate testing approaches Approaches: Two separate testing approaches

were implemented in the study for evaluating the were implemented in the study for evaluating the performance of each of the ramp control performance of each of the ramp control measures-measures-

1.1. Fixed Increment: The mainline traffic being increased from Fixed Increment: The mainline traffic being increased from base volume by 500 veh/hr and 1000 veh/hr. base volume by 500 veh/hr and 1000 veh/hr.

2.2. Percentage Increment: Both the mainline and the ramp Percentage Increment: Both the mainline and the ramp volumes were increased by 5%, 10% and 15% of the base volumes were increased by 5%, 10% and 15% of the base volume on the mainline and ramp respectively.volume on the mainline and ramp respectively.

► For both the test scenarios, the mainline For both the test scenarios, the mainline performance in each of the four control methods performance in each of the four control methods was evaluated with respect to:was evaluated with respect to:

1.1. Mainline Weighted Travel TimeMainline Weighted Travel Time2.2. Mainline Weighted Travel SpeedMainline Weighted Travel Speed3.3. Mainline Weighted Travel DelayMainline Weighted Travel Delay

Results – Mainline Travel TimeResults – Mainline Travel Time

► ALINEA provided ALINEA provided the lowest the lowest mainline travel mainline travel time under all time under all traffic volume traffic volume conditions.conditions.

► Fixed Time Fixed Time metering metering provided very provided very close close performance in performance in terms of mainline terms of mainline travel time.travel time.

-20.00%

-15.00%

-10.00%

-5.00%

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE

Base Volume Base Volume + 500 Base Volume + 1000

Percentage Change (From Base Condition) Percentage Change (Travel Time Change from No Metering - Same Volume)

Results – Mainline Travel SpeedResults – Mainline Travel Speed

► ALINEA provides the ALINEA provides the highest mainline highest mainline travel speed even in travel speed even in high traffic high traffic volumes, almost volumes, almost close to 33 mph at close to 33 mph at 15% higher 15% higher mainline volumes.mainline volumes.

► ZONE proved to be ZONE proved to be the least effective the least effective ramp control ramp control mechanism in the mechanism in the study corridor.study corridor.

-40.00%

-30.00%

-20.00%

-10.00%

0.00%

10.00%

20.00%

30.00%

No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE

Base Volume Base Volume + 500 Base Volume + 1000

Percentage Change (From Base Condition) Percentage Change (Travel Speed Change from No Metering under Same Volume)

Results – Mainline Travel DelayResults – Mainline Travel Delay

► In terms of mainline In terms of mainline travel delay ALINEA travel delay ALINEA performs best when performs best when the corridor is the corridor is operating at operating at additional 7% of additional 7% of base volume.base volume.

► At an additional At an additional 15% volume, 15% volume, ALINEA performs ALINEA performs marginally better. marginally better. Fixed time metering Fixed time metering performs at same performs at same level as open ramp.level as open ramp.

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%

No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE No RampMeter

Fixedtime

Meter

ALINEA ZONE

Base Volume Base Volume + 500 Base Volume + 1000

Percentage Change (From Base Condition) Percentage Change (Travel Delay Change from No Metering - Same Volume)

Consolidated Ramp Metering Consolidated Ramp Metering Measure PerformanceMeasure Performance

► Among the new control algorithms, ALINEA performs best in terms of all Among the new control algorithms, ALINEA performs best in terms of all measures of effectiveness (MOE).measures of effectiveness (MOE).

► Additional test conditions involving the increment in the mainline and the on-Additional test conditions involving the increment in the mainline and the on-ramp volume by 5%, 10% and 15% of the current (base) volume were also ramp volume by 5%, 10% and 15% of the current (base) volume were also simulated. ALINEA proved to have a similar performance over other ramp simulated. ALINEA proved to have a similar performance over other ramp control measures.control measures.

► Fixed Time metering as implemented by IDOT currently, provides good Fixed Time metering as implemented by IDOT currently, provides good control at traffic demand levels.control at traffic demand levels.

► In the study, ZONE performs poorly with respect to MOEs in spite of its In the study, ZONE performs poorly with respect to MOEs in spite of its inherent strengths. One reason for this is the close spacing of the on-ramps inherent strengths. One reason for this is the close spacing of the on-ramps and the general geometry and traffic characteristics of Dan Ryan. and the general geometry and traffic characteristics of Dan Ryan.

► Overall, ramp metering is justifiable. Depending on local conditions and Overall, ramp metering is justifiable. Depending on local conditions and control measures implemented, the benefits can be quantified as:control measures implemented, the benefits can be quantified as:

1.1. Reduction in mainline travel delay by 10% to 50%.Reduction in mainline travel delay by 10% to 50%.2.2. Reduction in mainline travel time by 7% to 19%.Reduction in mainline travel time by 7% to 19%.3.3. Increase in the mainline travel speed by 5% to 22%.Increase in the mainline travel speed by 5% to 22%.4.4. Provide a equitable balance between mainline traffic flow and traffic inflow from Provide a equitable balance between mainline traffic flow and traffic inflow from

on-ramps.on-ramps.

Optimum Fixed Green Time for Optimum Fixed Green Time for HGV Operations - BackgroundHGV Operations - Background

► FHWA national VMT statistics have FHWA national VMT statistics have shown the following key facts shown the following key facts regarding HGV operations in the regarding HGV operations in the country since 1980:country since 1980:

1980 – 1995: 58.2% increase for 1980 – 1995: 58.2% increase for Passenger Vehicles (PV) and 64.2% Passenger Vehicles (PV) and 64.2% increase for trucks (HGV); Combination increase for trucks (HGV); Combination HGV shows a 68.1% increase.HGV shows a 68.1% increase.

1995 – 1999: 10.9% increase for PV and 1995 – 1999: 10.9% increase for PV and 13.8% increase for HGV; Combination 13.8% increase for HGV; Combination HGV shows a 14.7% increase.HGV shows a 14.7% increase.

1999 – 2003: 7.6% increase for PV and 1999 – 2003: 7.6% increase for PV and 6.5% increase for HGV; Combination 6.5% increase for HGV; Combination HGV shows a 4.5% increase.HGV shows a 4.5% increase.

► The figures absolutely prove that truck The figures absolutely prove that truck travel is outgrowing passenger car travel is outgrowing passenger car travel in terms of VMT and this trend is travel in terms of VMT and this trend is going to continue with economic going to continue with economic growth and GDP growth.growth and GDP growth.

► It is therefore required to cater to the It is therefore required to cater to the demands of the growing truck demands of the growing truck population on the nations highways.population on the nations highways.

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

1980 - 1995 1995 - 1999 1999 - 2003

PV Trucks Consolidated HGV

HGV Operation – Simulation HGV Operation – Simulation ObservationsObservations

► During the simulation runs, it was visually observed:During the simulation runs, it was visually observed:

Current fixed green times 1.5 sec was insufficient for HGVs, that have Current fixed green times 1.5 sec was insufficient for HGVs, that have stopped at the ramp signal head, to accelerate and merge with the stopped at the ramp signal head, to accelerate and merge with the mainline traffic.mainline traffic.

In case of high HGV volume ramps, this led to queue buildup on the ramp In case of high HGV volume ramps, this led to queue buildup on the ramp with faster moving passenger cars waiting behind and spilling back into with faster moving passenger cars waiting behind and spilling back into arterial network.arterial network.

► To counter this, several measures can be taken like:To counter this, several measures can be taken like:

HGV Specific LanesHGV Specific Lanes – Ideal for segregation of traffic but involves major – Ideal for segregation of traffic but involves major capital investment in terms of new design and construction.capital investment in terms of new design and construction.

Priority Signal for HGVPriority Signal for HGV – Dynamic method of altering the green signal – Dynamic method of altering the green signal timing depending on the detection of HGV. But this involves timing depending on the detection of HGV. But this involves implementation of adaptive signaling methods.implementation of adaptive signaling methods.

Altering Fixed Green TimeAltering Fixed Green Time – Least expensive method of enabling a – Least expensive method of enabling a smooth HGV flow. It can have adverse effects on the mainline and so smooth HGV flow. It can have adverse effects on the mainline and so careful study is required to justify the trade-off.careful study is required to justify the trade-off.

► The effect of altering the on-ramp fixed green time has been The effect of altering the on-ramp fixed green time has been analyzed in this study.analyzed in this study.

HGV Operation Study HGV Operation Study FrameworkFramework

► Study was conducted on the 63Study was conducted on the 63rdrd street on-ramp which, as street on-ramp which, as per the traffic volume data from IDOT, has the highest HGV per the traffic volume data from IDOT, has the highest HGV volume.volume.

► The current base volume of HGV on the 63The current base volume of HGV on the 63rdrd street on-ramp street on-ramp is around 6% of the total traffic volume.is around 6% of the total traffic volume.

► The test scenarios intended to test the mainline and ramp The test scenarios intended to test the mainline and ramp performance in terms of:performance in terms of:

1.1. Average mainline and ramp travel time.Average mainline and ramp travel time.2.2. Average mainline and ramp travel speed.Average mainline and ramp travel speed.3.3. Average mainline and ramp travel delay.Average mainline and ramp travel delay.

► The ramp HGV volume was increased 5% and the The ramp HGV volume was increased 5% and the performance was measured with the HGV volume at base, performance was measured with the HGV volume at base, 5%, 10% and 15% of the total ramp traffic volume.5%, 10% and 15% of the total ramp traffic volume.

► The fixed green time on the ramp signal head was increased The fixed green time on the ramp signal head was increased from the base timing of 1.5 sec in intervals of 0.5 sec till 3.0 from the base timing of 1.5 sec in intervals of 0.5 sec till 3.0 sec, and the system performance was tested at 1.5 sec, 2.0 sec, and the system performance was tested at 1.5 sec, 2.0 sec, 2.5 sec and 3.0 sec fixed green time.sec, 2.5 sec and 3.0 sec fixed green time.

HGV Operation Study ResultsHGV Operation Study Results► Based on the simulation runs, for varying levels of HGV volumes on Based on the simulation runs, for varying levels of HGV volumes on

the 63the 63rdrd street ramp, the following results were obtained for the MOEs: street ramp, the following results were obtained for the MOEs:

Consolidated Travel Time - 63rd On-Ramp (sec)

 

Consolidated Travel Time - Study Corridor (sec)

 Fixed Time Green

 Fixed Time Green

1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec 1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec

On-Ramp HGV

Volume

Base 73.09 62.46 34.62 58.49

On-Ramp HGV

Volume

Base 162.12 163.12 175.71 164.48

Base + 5% 81.43 63.45 35.04 57.59 Base + 5% 162.35 163.98 180.85 167.05

Base + 10% 89.15 64.18 37.87 56.74 Base + 10% 162.28 164.44 178.85 166.43

Base + 15% 93.91 64.78 40.17 56.47 Base + 15% 161.05 164.47 192.35 168.74

Consolidated Travel Speed - 63rd On-Ramp (mph)

 

Consolidated Travel Speed - Study Corridor (mph)

 Fixed Time Green

 Fixed Time Green

1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec 1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec

On-Ramp HGV

Volume

Base 5.4 6.3 11.5 6.8

On-Ramp HGV

Volume

Base 35.1 34.9 32.4 34.6

Base + 5% 4.9 6.2 11.4 6.9 Base + 5% 35.0 34.7 31.5 34.1

Base + 10% 4.4 6.2 10.5 7.0 Base + 10% 35.1 34.6 31.8 34.2

Base + 15% 4.2 6.1 9.9 7.0 Base + 15% 35.3 34.6 29.9 33.7

Consolidated Travel Delay - 63rd On-Ramp (sec)

 

Consolidated Travel Delay - Study Corridor (sec)

 Fixed Time Green

 Fixed Time Green

1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec 1.5 Sec 2.0 Sec 2.5 Sec 3.0 Sec

On-Ramp HGV

Volume

Base 59.8 49.2 21.3 45.2

On-Ramp HGV

Volume

Base 29.8 30.7 43.0 32.1

Base + 5% 68.1 50.1 21.7 44.3 Base + 5% 30.2 31.7 48.0 34.6

Base + 10% 75.8 50.9 24.6 43.5 Base + 10% 30.2 32.1 46.0 34.0

Base + 15% 80.6 51.5 26.9 43.2 Base + 15% 29.0 32.2 59.6 36.3

HGV Study – ConclusionsHGV Study – Conclusions► From the consolidated results tabulated above it can From the consolidated results tabulated above it can

be concluded that:be concluded that:

For the traffic and geometric specific to the 63For the traffic and geometric specific to the 63rdrd street on street on ramp, a 2.0 sec fixed green time provides the maximum ramp, a 2.0 sec fixed green time provides the maximum equitable benefits in terms of on-ramp and mainline travel equitable benefits in terms of on-ramp and mainline travel time, speed and delay. time, speed and delay.

► Data thus obtained from the simulation runs provides Data thus obtained from the simulation runs provides a policy tool for altering the fixed green time on the a policy tool for altering the fixed green time on the ramps depending on the local traffic conditions.ramps depending on the local traffic conditions.

► However, it is required to prioritize the severity of the However, it is required to prioritize the severity of the impact on the on-ramp and the mainline. Only after impact on the on-ramp and the mainline. Only after careful study and cost analysis of both the positive careful study and cost analysis of both the positive and negative impacts of the changes should the and negative impacts of the changes should the green time be altered. green time be altered.

Summary of Study ResultsSummary of Study Results► Based on algorithm study conducted on the Dan Ryan, the Based on algorithm study conducted on the Dan Ryan, the

following results can be concluded:following results can be concluded:

Ramp metering absolutely improvement in the overall network Ramp metering absolutely improvement in the overall network performance with respect to travel time, travel speed and travel delay performance with respect to travel time, travel speed and travel delay over no-metering scenario as can be summarized as below:over no-metering scenario as can be summarized as below:

1.1. Reduction in mainline travel delay by 10% to 50%.Reduction in mainline travel delay by 10% to 50%.2.2. Reduction in mainline travel time by 7% to 19%.Reduction in mainline travel time by 7% to 19%.3.3. Increase in the mainline travel speed by 5% to 22%.Increase in the mainline travel speed by 5% to 22%.4.4. Provide a equitable balance between mainline traffic flow and traffic inflow Provide a equitable balance between mainline traffic flow and traffic inflow

from on-ramps.from on-ramps.

The degree of improvement depends on the local traffic and geometric The degree of improvement depends on the local traffic and geometric conditions.conditions.

The overall performance of the ramp control measures can be ranked The overall performance of the ramp control measures can be ranked as:as:

1.1. Coordinated ALINEACoordinated ALINEA2.2. Fixed Time MeteringFixed Time Metering3.3. ZONEZONE

Under the current traffic volume condition, the IDOT metering rate of 1.5 Under the current traffic volume condition, the IDOT metering rate of 1.5 sec green time at the study site performs well. But with increasing sec green time at the study site performs well. But with increasing mainline volumes, as was observed, the performance of fixed time mainline volumes, as was observed, the performance of fixed time metering deteriorates and other alternative methods of ramp control metering deteriorates and other alternative methods of ramp control need to be considered.need to be considered.

Summary of Study ResultsSummary of Study Results……

contdcontd

► Based on the HGV study conducted, the Based on the HGV study conducted, the following can be concluded:following can be concluded:

Under the current HGV volumes, a fixed Under the current HGV volumes, a fixed green time of 1.5 sec provides acceptable green time of 1.5 sec provides acceptable levels of performance.levels of performance.

With increase in HGV volumes, both the With increase in HGV volumes, both the ramp and mainline performance is going to ramp and mainline performance is going to deteriorate and thus it is required to deteriorate and thus it is required to increase the fixed green time. increase the fixed green time.

A 2.0 sec fixed green time provides an A 2.0 sec fixed green time provides an equitable balance between the mainline equitable balance between the mainline and ramp performance.and ramp performance.