Modeling Study Estimates Connected and Automated Vehicles Reduce Fuel Consumption by Up to 18 Percent Using Microscopic Vehicle Trajectory Data.
The Simulation Study Used Empirical Vehicle Trajectory Data to Evaluate Connected and Automated Vehicles to Smooth Out Traffic Disturbances on a Freeway.
Emeryville, California, United States
Safe and Efficient Automated Freeway Traffic Control
Summary Information
While shockwaves naturally occur in freeway traffic, they present one of the largest safety risks on freeways since drivers do not expect to encounter abrupt drops in speed or stopped traffic. The objective of this study was to take typically unstable queued traffic and convert it to a steady flow while queued, thereby eliminating unexpected speed drops, and consequently reduce fuel consumption. The methodology assumed that all vehicles were connected and communicated their status (location and speed) to all other vehicles. The goal was to unify states across vehicles to anticipate and respond to long-range disruptions effectively. This forward-looking approach allowed the system to detect and dampen shockwaves, resulting in smoother conditions for safety and efficiency. The methodology was demonstrated with microscopic vehicle trajectory data on I-80 in Emeryville, CA, from genuine shockwaves in human-driven vehicle traffic as both the beginning conditions and the system's response restrictions.
METHODOLOGY
The study used vehicle trajectories reextracted from the NGSIM I-80 video recorded in Emeryville, CA in lane 2. Assuming all vehicles in the trajectories were connected human-driven vehicles (cHDVs), the study identified lead vehicles and repeated a process of “sampling the current traffic state to estimate the leader’s trajectory and then setting the CAV speed to intersect the perfect follower trajectory at the furthest point downstream” at each time step. The analysis scenarios included three different look ahead distances at 1,000 ft, 1,800 ft and 2,800 ft, and with different three acceleration conditions: (i) unlimited, (ii) one MPH per second maximum, and (iii) 0.5 MPH per second maximum.
FINDINGS
- All analysis scenarios (i.e., different look ahead distances and accelerations) showed that the CAV was able to nullify a stop wave with an acceleration reaching -8 MPH per second before reaching another vehicle, suggesting the potential in greatly reducing the risk of rear-end collisions.
- Fuel consumption reduced between 14 and 18 percent in all scenarios.
- At 0.5 MPH per second maximum acceleration, the reduction in fuel consumption were the most significant.
