The Transportation Division manages the planning, design, operation, maintenance, and improvements of the County Maintained Road System (CMRS) that currently includes approximately 2,500 miles of roadways. Major activities are administration, planning, design, construction, and traffic operations. Management and technical activities are centered in the City of San Bernardino office. Maintenance functions are provided through 13 yards with regional facilities located to best serve the 20,000-square-mile area of the County.

Routine maintenance activities of the Department include: patching and crack filling of approximately 6,000 lane miles of asphalt pavement; grading of 421 miles of unpaved roads; shoulder maintenance; plowing snow on approximately 450 miles of mountain roads; traffic signal maintenance at 50 intersections; roadside weed abatement in urban areas; traffic signs, and pavement striping maintenance throughout the system; maintenance of bridges, metal pipe and concrete box culverts; maintenance of drainage facilities and guardrails; and storm repairs and clean up.

Many other road improvements are accomplished through cooperative efforts with other public agencies. Such cooperation provides funding opportunities and efficiency, as well as improved services to the traveling public. Agencies involved in such efforts are cities within the county, special districts, federal, state, regional agencies, and utility companies.