There are many sources of information about Signal Timing Design on the Internet. You might want to further your education by taking advantage of these resources.

National Transportation Library: Traffic Control Devices
http://www.bts.gov/ntl/subjects/traff-devices.html

Traffic Signal links from Darcy Bullock, Purdue University
http://ce.ecn.purdue.edu/~darcy/signalequipment.htm

Transportation Research Board Traffic Signal Systems Committee
http://www.engr.utk.edu/~signal/

Texas DOT Traffic Operations Division
http://www.dot.state.tx.us/insdtdot/orgchart/trf/trf.htm

CalTrans Transportation Laboratory
http://tresc.dot.ca.gov/hq/esc/Translab/intro.htm

CalTrans District 11 Traffic Signal Operations
http://www.dot.ca.gov/dist11/operations/cfeaver.htm

CalTrans Traffic Manual Online
http://www.dot.ca.gov/hq/traffops/signtech/signdel/