Costs tend to go up during transportation projects, making it hard for State Departments of Transportation to stick to budgets. This paper looks at ways to estimate and manage costs better. They studied what other states do and talked to experts. They found that key areas for cost management include analyzing risks, predicting cost increases, making accurate initial estimates, and reviewing construction plans. States like Minnesota, California, Texas, Ohio, and Washington have good practices for setting reliable cost estimates. This paper brings together the best ways that different states manage costs for transportation projects in the U.S.