Effect of Electronically Enhanced Driver Behavior on Freeway Traffic Flow Alain L. Kornhauser Professor, Operations Research & Financial Engineering Director, Transportation Research Program Princeton University Presented at 53 rd Annual Meeting Transportation Research Forum Tampa, Fl March, 2012 Scott H. Chacon Analyst, Wells Fargo Investment Banking and

Overview Well known: congestion is made worse by variations in how drivers react to vehicles ahead – lane changing and as well Thus, augmenting Driver Behavior may improve Traffic Flow What can augment Driver Behavior: – Most near-term realizable Driver Behavior augmentation is via intelligent cruise control – Already does it on low density freeways: Non-rigorous evidence that travel times have reduced for because speeds is constant

Overview Investigated: extent to which intelligent cruise control-type augmentation of driver behavior can improve traffic flow. Shown: if intelligent cruise control constrains vehicles from getting too close together, especially in stop and go traffic, the frequency of the formation of traffic shock waves is significantly reduced resulting in higher traffic flow and shorter travel times. Compared are minimum time-headway and minimum separation intelligent cruise control based augmentations of driver behavior. Also Identified: – the optimal minimum following distance – The reduction in travel time

Micro Simulation of Traffic Flow Used is extended version of: – Longitudinal behavior: Triber et al. (2000) Intelligent Driver Model (IDM) – Lane change behavior: Kesting et al. (2007) Minimizing Overall Braking decelerations Induced by Lane-changes (MOBIL) Implemented over – 4-lane, 3,000 meter stretch of freeway in Pasadena, Ca. – Segment chosen because of the ready availability of loop detector data from the Performance Measurement System (PeMS) Vehicle flow, occupancy and speed by lane in 4 locations plus entrance and off ramps

The Freeway Segment Eastbound I-210 Btwn Lake Blvd & N. Sierra Madre Blvd. – Loop Detectors in each of the 4 lanes before Lake Blvd., N. Hill Ave., N. Allen Ave & Sierra Madre Blvd. – On-ramp Loop Lake, Hill and Sierra Madre – Off-ramp Loop Hill, S. Altadena and Sierra Madre

Modification of Micro Simulation Expanded to include – 4 lanes (substantial addition) – Multiple on and off ramps (major addition) – Minimum following distance driver behavior augmentation – UI changes to allow: Switch between two simulations: – Use Observed Ramp Data » Used for calibrating driver behavior so as to have simulation replicate the observed PeMS observations – Set All Variable Manually » Ability to select values for 11 parameters Upstream in-flow, in-flow & out-flow at each ramp, lane- change politeness, speed of simulation and minimum allowable distance. Output plots of absolute and relative-to-observed flows in each lane at each station

Modification of Micro Simulation

Calibration of Micro Simulation Done over a 24 hour period to match real data (Sept 22, 2008) – Each new vehicle appropriately assigned a “destination” (off-ramp or continue on I-210) – A right-bias incentive to change lanes behavior was added to exiting vehicles. Proportional to the number of lanes that need to be changed and nversely proportional to Distance-to-Exit Output – Driver behavior distributions for which simulated outflow ~ Actual outflow

Calibrated Parameters of Micro Simulation ParameterCar nominal valueTruck nominal value Desired Velocity (v 0 )140 km/h100 km/h Time headway (T)1.5 Sec1.7 Sec Min Gap (s 0 )2.0 m Acceleration (a max )0.3 m/s 2 Deceleration (d max )3.0m/s 2 2.0m/s 2 Input: & On-Ramps w destinations matching off-ramps and station Input: & On-Ramps w destinations matching off-ramps and station Parameters Calibrated to match: , , & Off-Ramps Parameters Calibrated to match: , , & Off-Ramps

Observed Flows I-210 Hour of day Off-Ramp On-Ramp

% Error in Flow Since Midnight Since Midnight

Flow Implications of Cruise Control Augmentation of Driver Behavior Previous studies by Ionnou & Chien (1993) & Arem (2006) – Constant minimum time headway (min separation proportional to distance ensuring safety) smoothes traffic flow and increases flow rate (in single lane) What about: Reliance on “normal” Driver Behavior; except, as it might encroach on some Minimum Separation constraint – Deceleration Behavior of closing vehicles (V trailing > V leading ; S > S min ) Controlled by intelligent cruise controller so as to achieve a feedback- controlled minimum separation, S = S min at V trailing = V leading – S min = 0 is equivalent to zero augmentation of Driver Behavior, e.g. existing condition

Flow Improvement for various Separation Distance Average Flow Improvement at peak times over pure Driver Behavior (no augmentation)

Average Flow Improvement v Minimum Separation Distance Average Flow Improvement at peak times over pure Driver Behavior (no augmentation) 10 meters

Improvement in Travel Time v Min Separation Cumulative Distributions of Travel time for all vehicles traveling the whole length (from to )

While simulation was done for only one freeway segment and only one day’s demand – Does indicate that augmenting driver behavior using minimum separation does reduce the formation of shocks in the traffic flow. Conclusions

Thank You