  A rapidly deployable and cost-effective railroad crossing early warning
system integrated with the railway system is attractive due to its protection
of the unmanned grade crossings, which requires a warning system with
long-distance communication link. In this paper, we investigate the problem of
suitable antenna selection for such a railway warning system First, the antenna
criteria for railroad crossing safety applications are described based on
practical system considerations, the safe distances on the road and on the
railway. Then, the optimal antenna pattern is derived theoretically to get the
smallest size which fits for the practical installation. We also conducted a
feasibility study of an array antenna through measurements on a near field
scanner.
