Because this is a construction project, the logo should work on large signage / billboards. The literal words "Measure T" should be incorporated. Because this is a local government project, the logo shouldn't be too informal -- no Comic Sans. Graphics involving roads, construction workers, bright colors
Some marketing samples we've seen can be found in this PDF:
http://nctpa.legistar.com/gateway.aspx?M=F&ID=259f7772-1c82-49cf-bf52-cd1264ae6435.pdf