Japan's lack of space was so critical that introducing a superb public transportation system for both intra- and inter-city use just wasn't enough. Stringent transportation policies were implemented alongside public transport initiatives. In addition, Japan recognised that, in order for them to be effective, it would need to throw in incentives and disincentives. The single act that caused an explosive growth in the Japanese microscopic car population was "Kei-Jidosha", or k-class (light class) car, legislation. It specified that cars which are less than a certain length and breadth with an engine capacity and power output below a certain limit can be registered for use, even if their owners do not have a private, off-the-road parking space for their exclusive use. In addition, k-cars were excused from excessive tax surcharges and inner city parking fines.