  There are different proposals in the literature on how to protect pedestrians
using warning systems to alert drivers of their presence. They can be based on
onboard perception systems or wireless communications. The evaluation of these
systems has been focused on testing their ability to detect pedestrians. A
problem that has received much less attention is the possibility of generating
too many alerts in the warning systems. In this paper, we propose and analyze
four different algorithms to take the decision on generating alerts in a
warning system that is based on direct wireless communications between vehicles
and pedestrians. With the algorithms, we explore different strategies to reduce
unnecessary alerts. The feasibility of the implementation of the algorithms was
evaluated with a deployment using real equipment, and tests were carried out to
verify their behavior in real scenarios. The ability of each algorithm to
reduce unnecessary alerts was evaluated with realistic simulations in an urban
scenario, using a traffic simulator with vehicular and pedestrian flows. The
results show the importance of tackling the problem of driver overload in
warning systems, and that it is not straightforward to predict the load of
alerts generated by an algorithm in a large-scale deployment, in which there
are multiple interactions between vehicles and pedestrians.
