An efficient management system for parking lots and traffic monitoring in a metropolitan city is a very important issue, which is tightly closed to qualify of life. While a residential permit parking program has been contributing to resolve the lack of parking places, there has been no autonomous authentication system due to no apparent entrance gate and smallness of each parking zone. In this paper, we propose and implement an authentication system for residential permit parking lot using wireless sensor networks, which is cost-effective and even no need for additional managing person. Through the experimental evaluation, we analyzed relationship between the life time of sensor nodes and the various values of sleep periods to minimize power consumption of the nodes, and also showed that the difference of luminance sensed by each sensor node is at least 45 or bigger between when the parking place is occupied or not, resultingly it can be used to decide whether a parking place is occupied or not by simply detecting the change of luminance sensed.