This report describes the application of a computer-based traffic network model to a set of synthetic test networks, to examine the effects of lower speed limits on traffic progression, travel times, speeds and delays, fuel consumption and emissions under different traffic control strategies and levels of traffic congestion. It suggests that although travel times increase with lower speed limits, the increases are proportionately less than those indicated by the differences between speed limits. Further there are indications that intelligent traffic signal coordination systems may further ameliorate such increases.