The authors note that the analysis reported in this paper did not account for temporal trends in pedestrian injury nor the effects of seasonality on injury risk. As a consequence, the results may be biased in magnitude or direction. A revised analysis using more sophisticated methodology, accounting for time trends and seasonal influences, has been published and is available here:
Richmond, Willan, Rothman, et al. The impact of pedestrian countdown signals on pedestrian-motor vehicle collisions: a reanalysis of data from a quasi-experimental study. Inj Prev Published Online First: 23 Sept 2013. doi:10.1136/injuryprev-2012-040717.