(of motor vehicles) the quality of being fit to drive on the open road WordNet 3.0 & Open English WordNet

Roadworthiness or streetworthiness is a property or ability of a car, bus, truck or any kind of automobile to be in a suitable operating condition or meeting acceptable standards for safe driving and transport of people, baggage or cargo in roads or streets, being therefore street-legal. Wikipedia

The property of being roadworthy. Wiktionary

Property of being roadworthy. Wiktionary (translation)