Transportation Planning 111 Congresses 68 History 55 Research 51 Mathematical models 48 Transportation and state 48 Local transit 39 Roads 30 Passenger traffic 28 Traffic engineering 28 Urban transportation 26 Hazardous substances 23 Railroads 23 Environmental aspects 22 Safety measures 22 Law and legislation 20 Urban transportation policy 19 City planning 18 Finance 17 Periodicals 17 Communication and traffic 16 Freight and freightage 16 Storage 15 Economic conditions 14 People with disabilities 14 Data processing 13 Economic aspects 13 Automation 12 Cost effectiveness 12