The county's 3-Year Transportation Improvement Plan provides an expenditure plan for local road improvements funded by the county's 1/2 cent transportation sales tax. The projects listed below include those currently under construction and those to be funded through 2009.

• City of Dardenne Prarie
• City of Lake Saint Louis
• City of O'Fallon
• City of Saint Charles
• City of Saint Peters
• City of Weldon Springs
• City of Wentzville
• Saint Charles County Highway Department