rheologyrheostatrhyoliteribrib domerib to prevent seepageribbedribbed barribbed boltribbed flatribbed floorribbed panelribbed slabribbonrice husk aggregaterich concreterich limerich mixrichnessriddlerideriderrider comfortridershipridgeridge canalridge gusset plateridingriding comfortriffleriftrift valleyrigriggingright angleright angle accidentright angle collisionright angle crossingright angle parkingright angle parking arrangementright bankright exitright hand exitright hand mergeright handedright handed coordinate systemright of wayright of way widthright turnright turn lane