Roads 198 Pavements 154 Design and construction 151 Highway engineering 106 Traffic signs and signals 100 Road materials 86 Testing 74 Electronic traffic controls 70 Maintenance and repair 65 Pavements, Asphalt 65 Traffic engineering 61 Safety measures 55 Pavements, Asphalt concrete 40 Intelligent transportation systems 35 Traffic safety 32 Vehicular ad hoc networks (Computer networks) 32 Asphalt 31 Pavements, Concrete 23 Automobiles 21 Performance 20 Programmable controllers 20 Bitumen 19 Interchanges and intersections 19 Pavements, Flexible 18 Recycling 18 Subgrades 18 Waste products as road materials 16 Bituminous materials 15 Foundations 15 Analysis 13