  This paper evaluates the performance of ETSI ITS Contention-Based Forwarding
(CBF) and ETSI Simple GeoBroadcast forwarding while disseminating warning
messages over a Geographical Area in highway and urban scenarios. Our
experimental evaluation considers the complete ETSI ITS architecture including
the Decentralized Congestion Control (DCC) mechanism. We propose an enhanced
CBF mechanism, named S-FOT+, which combines several improvements to the ETSI
CBF algorithm. S-FoT+ has a similar or better performance than the ETSI
forwarding algorithms regarding both reliability and end-to-end delay while
requiring much fewer transmissions. The improvements are equally effective and
efficient in both urban and highway scenarios with large Destination Areas.
Finally, we evaluate the trade-offs that stem from using multi-hop broadcast
mechanisms in urban settings with smaller Destination Areas when compared to
single-hop broadcast. Results show that multi-hop mechanisms significantly
improve coverage at the cost of an increased number of transmissions.
