Improving signal timing has about the best benefit/cost ratio of any improvement the traffic engineering community can make. Back in 2005, a bunch of agencies collaborated to put together the National Traffic Signal Report Card. The second edition was released in 2007 and now the group is polling all agencies involved with traffic signal timing to assemble the third edition.
According to the report card, the United States went from a D- in 2005 to a D in 2007. The 2007 report highlighted case studies of how agencies could make small (cheap) changes to raise their grades several levels. Traffic engineers need to use reports like these to educate their policy makers on the huge traffic management benefits of having well maintained traffic signal operations so budgets can support these efforts.
If you are involved with traffic signal timing, I hope you'll spend the time to fill out the assessment here.
