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The Scientific World Journal
Volume 2014, Article ID 923632, 9 pages
Research Article

Robust Range Estimation with a Monocular Camera for Vision-Based Forward Collision Warning System

Department of Electronic Engineering, Sogang University, CPO. Box 1142, Seoul 100-611, Republic of Korea

Received 30 August 2013; Accepted 22 October 2013; Published 16 January 2014

Academic Editors: G. Berrettini and A. Lahiri

Copyright © 2014 Ki-Yeong Park and Sun-Young Hwang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We propose a range estimation method for vision-based forward collision warning systems with a monocular camera. To solve the problem of variation of camera pitch angle due to vehicle motion and road inclination, the proposed method estimates virtual horizon from size and position of vehicles in captured image at run-time. The proposed method provides robust results even when road inclination varies continuously on hilly roads or lane markings are not seen on crowded roads. For experiments, a vision-based forward collision warning system has been implemented and the proposed method is evaluated with video clips recorded in highway and urban traffic environments. Virtual horizons estimated by the proposed method are compared with horizons manually identified, and estimated ranges are compared with measured ranges. Experimental results confirm that the proposed method provides robust results both in highway and in urban traffic environments.