Vehicle Platooning Impact on Drag Coefficients and Energy/Fuel Saving Implications

TL;DR

This study develops models to quantify how vehicle position and spacing in platoons affect drag and fuel savings, revealing significant potential reductions for trucks and buses at typical following distances.

Contribution

The paper introduces empirical power models linking vehicle position and gap to drag coefficients and fuel savings across different vehicle types.

Findings

Fuel savings of 4.5% for light duty vehicles at 0.5 sec gap

15.5% fuel reduction for buses at optimal gap

Significant fuel savings for trucks even at longer gaps

Abstract

In this paper, empirical data from the literature are used to develop general power models that capture the impact of a vehicle position, in a platoon of homogeneous vehicles, and the distance gap to its lead (and following) vehicle on its drag coefficient. These models are developed for light duty vehicles, buses, and heavy duty trucks. The models were fit using a constrained optimization framework to fit a general power function using either direct drag force or fuel measurements. The model is then used to extrapolate the empirical measurements to a wide range of vehicle distance gaps within a platoon. Using these models we estimate the potential fuel reduction associated with homogeneous platoons of light duty vehicles, buses, and heavy duty trucks. The results show a significant reduction in the vehicle fuel consumption when compared with those based on a constant drag coefficient assumption. Specifically, considering a minimum time gap between vehicles of $0.5 \; secs$ (which is typical considering state-of-practice communication and mechanical system latencies) running at a speed of $100 \; km/hr$, the optimum fuel reduction that is achieved is $4.5 \%$, $15.5 \%$, and $7.0 \%$ for light duty vehicle, bus, and heavy duty truck platoons, respectively. For longer time gaps, the bus and heavy duty truck platoons still produce fuel reductions in the order of $9.0 \%$ and $4.5 \%$, whereas light duty vehicles produce negligible fuel savings.