The Timeslot Boundary Synchronization Problem occurs when timeslot boundaries become aligned leading to an increase in the probability of message collisions. This alignment, which can occur in Vehicular Ad Hoc Networks using the 802.11p protocols, adversely affects the performance of multi-hop message broadcasts. This paper describes the causes of this phenomenon and describes link and network layer design guidelines to address the problem. An integrated simulation system, which combines widely used wireless network and microscopic vehicle simulators, was used to simulate multi-hop emergency message broadcast in dense traffic situations. The simulation results show that addressing the Timeslot Boundary Synchronization Problem can reduce the total latency of multi-hop messages by 20.3% to 26.6%.