The parking space race: SENSIT wireless parking sensors for vehicle detection

With the onset of mobile parking and more advanced systems to regulate traffic within cities, the need for timely information about parking availability is more acute than ever. We have probably all experienced driving around in circles looking for a parking space. Although guidance to available spaces within multistorey car parks is becoming more common, generally the majority of parking availability is to be found on the street.

To date, though, few cities have implemented a guidance system to direct traffic to these spaces, even though there is much to gain from doing so. Benefits include better traffic flow, reduced pollution, and last but not least, reduced frustration on the part of those drivers seeking a space. Additionally, local authorities can impose fines for overstays more efficiently.

The above benefits can be achieved with an active parking guidance system, based on wireless sensors in every parking space, which can detect the presence of a car in the space and note the arrival time of that particular vehicle.

Singapore deployment

A good example of such a system is found at the Holland Village parking facility in Singapore. This car park is extensively used throughout the day and night to serve customers of the local shops, bars, and restaurants, so a parking guidance system was implemented to guide traffic to available spaces. As the majority of the spaces are outdoors, requirements were established to ensure the system could monitor the occupancy status of the 190 spaces. The owner of the facility, the Housing and Development Board (HDB), was adamant that customers should be able to find a space quickly, without causing congestion on nearby public roads.

Technologies normally employed within indoor car parks (such as ultrasonic sensors) could not be used in this case because every space would need to be wired, requiring a great amount of construction work. Temporary closure of the car park was not an option, so a completely wireless solution was sought. To meet the high requirements set by the HDB, Nedaps wireless space-count system was selected. The system was integrated and installed by Sun Japan Systems.

The solution is based on SENSIT, a wireless sensor provided by Nedap that is mounted into the floor of every parking space and operates without power wiring. It determines whether a space is occupied or not by detecting the presence of a vehicle based on a change in the Earths magnetic field and infrared detection. This dual-sensor technology and a special detection algorithm ensure the occupancy detection reliability is close to 100%. The sensors in the parking lot communicate wirelessly with centrally mounted relay nodes, which relay the information directly to the central parking guidance system.

As soon as a vehicle leaves, the status of the car park changes and a message is transmitted to indicate that the space is free. Based on the information from the sensor, the guidance system directs traffic to the zones within which there are available spaces. In the case of Holland Village, parking is divided into six zones; the system indicates to drivers on special displays how many spaces are available within every zone.

Overstay detection

In addition to the parking guidance functionality, the SENSIT sensors can also be used for overstay detection. The network of sensors is time synchronized, meaning that with every arrival and departure of a car, an occupied or available message is sent to the system, including an accurate timestamp. With the SENSIT wireless sensor network in place, the enforcement of overstay in time-limited parking facilities is simplified. When the maximum parking duration is exceeded in a specific bay, the system automatically sends a message to an attendant. The attendant will go to the specific bays in overstay, check on a mobile device if the same car is still overstaying, and issue a ticket.

When SENSIT wireless sensors are used in combination with parking meters, overstay fines for paid on-street parking can be enforced more efficiently. The sensor network knows how many spaces are occupied, and the parking meters know how many spaces are paid for at any specific moment. A central system can now alert attendants when there are parked cars in overstay. On location, attendants can check whether the car is still in overstay and write a ticket. With a SENSIT wireless sensor network in place, enforcement attendants do not need to check every car in a particular area; they are actively alerted when there are vehicles in overstay and are directly guided to them. In this way, on-street parking enforcement can be carried out in a cost-efficient manner, at the same time optimizing parking regulation.

Wireless platforms that detects vehicles occupancy in parking spots are also installed and in daily operation at Sainsburys supermarket car park in Slough, nearby London, in the UK and along the road at a truck parking facility in The Netherlands.