This paper proposes a topology independent, scalable information dissemination algorithm for spatio-temporal traffic information such as parking place availability using vehicular ad hoc networks (VANET) based on Wireless-LAN IEEE 802.11.The algorithm uses periodic broadcasts for information dissemination. Broadcast redundancy is minimized by evaluation of application layer information and aggregation. Due to the spatio-temporal characteristics of parking place information, the spatial distribution of information is limited by utilizing techniques, which take the local relevance and age of information into account.Based on a realistic model of a german city with up to 10000 vehicles, our results show that a decentralized parking place information system works efficiently even with 5% of vehicles equipped with Wireless-LAN and without the help of any message relaying infrastructure. This fact makes such a non-safety driver assistance application very interesting, especially in the rollout phase of vehicular ad hoc networks.