More efficient use of limited parking space with modern parking bay monitoring

2016-05-17 09:07

The current parking management situation for local authorities

Providing sufficient parking spaces for drivers whilst keeping city centres attractive is an important task for local authorities. Jobs in local businesses and city restaurants should be secured and not transferred to large shopping centres out of town. At the same time the increasing needs of the population for individual mobility and adherence to strict environmental laws (dust particles and CO2-emmissions) must be fulfilled. However, traffic areas can´t just be freely expanded and parking space in city centres is scarce. The portion of traffic looking for a parking space is already up to 30% of total traffic. Urbanization and ever increasing car registrations put local authorities in front of huge challenges. Introducing measures such as the expansion of public transport and the introduction of low emission zones will not be enough to avoid traffic jams and the time consuming search for parking spaces.

Goal: Less cars on the road with maximum utilization of underground garages and multi storeys

Market analysts estimate that around 75% of parking areas fall into the so called off-street category, i.e. parking spaces not on public roads. If you want to reduce the number of cars on the road the goal must be to put the available parking spaces in underground garages and multi-storey car parks to the best possible, use. Ideally people should only park on public roads when underground garages and multi-storey car parks are almost full. But in reality it isn’t that simple. Whilst drivers cruise around looking for an unoccupied space on the roads, there are countless vacant spaces in underground garages and multi-storey car parks staying empty. In the USA they are trying to improve the attractiveness of off-street parking to some extent by ensuring that off-street parking is always cheaper than on-street parking. Another possibility to improve the attractiveness of car parks is to increase the comfort for drivers.

Inner-city parking guidance signs should display the exact amount of vacant spaces and guide the driver to multi-storey car parks with vacant spaces. Under no circumstances must the number of spaces displayed on the inner city parking guidance signs differ from the actual occupancy of the car park. If only very few vacant places are displayed even though the garage is nearly empty, drivers will lose confidence in the technology. The opposite scenario, that drivers are lead to a supposed unoccupied space, which is in fact occupied will justifiably annoy the driver. In this case it is better to not have a parking guidance system than a misleading parking guidance system!

Having arrived in the car park the comfort for the driver is improved by leading him to the nearest vacant parking bay via dynamic arrow and numerical displays using LED technology. Furthermore, finding an individual space will be simplified by the use of distinct signals at each individual parking bay (green LED = vacant, red LED = occupied).

Conventional determination of parking garage occupancy

Public multi-storey car parks are mostly controlled with the help of a barrier system. By counting the number of times the barrier opens or impulses from the induction loops, the number of cars entering and exiting can be determined. This technology, though robust and well established, has great disadvantages. Every sensor inherently contains errors. For example, a manual opening of the barrier, or a car leaving the car park through the entry- instead of the exit-barrier, or two cars closely following each other being counted as one, or the induction loop mistakenly identifying a shopping trolley as a car, all these inevitably lead to a counting error. Even if this error is supposedly low, i.e. 1%, the impact on the correct assessment of the parking occupation is substantial.

Example of zone counting:

Let’s assume a multi-storey car park has 200 parking spaces and reaches maximum occupancy once daily. Thus there are 200 entries and exits each day, giving a total of 400 single counting operations. With a failure rate of 1% the resulting error is 4 cars per day. After 5 days the error could already be at 20 cars, which is 10% of the available parking capacity!

This error has an even greater impact if a lane- or level-counting system is used. If in our example the 200 parking spaces are distributed over 5 floors with 40 spaces each, then in the same scenario (maximum occupancy of the multi-storey once daily) the ground floor will count 200 entries and exits to the road. Furthermore 160 ascending and 160 descending from the higher lying floors are counted. Thus the occupancy of the ground floor is calculated from 720 counts. With a counting error of just 1% the error for the ground floor is 7,2 cars after just 1 day. Compared to the 40 spaces available at ground level this results in a counting error of up to 18% after just one day.

To correct these “cumulative counting errors” software algorithms are used, which regularly reset the occupancy level. However, this requires precise knowledge of the car park occupancy at a defined time. In the best case the car park is empty overnight so that the count value can be set back to zero. Although this is difficult when some of the spaces are let out on long time leases and the car park isn´t fully empty overnight. Particularly public car parks are often used 24 hours a day. So the operator has no alternative but to regularly determine the precise occupancy through counting by hand and entering the respective value into the system. Even the use of alternative technologies of car counting (such as optical barrier, ultrasound- or magnetic field sensors) won’t solve the problem. The cumulative error of zone counting is inherent in the system.

Characteristics of modern single space detection

In order to achieve maximum utilisation of the available spaces in a multi storey car park, the system must always show the correct number of vacant parking bays. The attractiveness of the car park is further increased by directing the drivers to the last available spaces. Only a modern single space detection system can accomplish this. Initially it is irrelevant which type of sensors are put to use. However, it is most important that every single space is monitored.

Example single space detection

A multi-storey car park has 200 spaces and achieves maximum occupancy once daily. The sensors of the single space detection system have measuring errors of 1%. This results in an error of 2 cars compared to the entire multi-storey car park. Also if a car isn´t detected properly, the error “heals” itself as soon as the car leaves the space. There are no cumulative errors inherent in the system as with the zone counting, for even after many years the maximum error count will remain at 1% (i.e. 2 cars). Even in the event of a total failure (for example a power cut in the  car park, or a deliberate switch off for maintenance purposes), every sensor in the system will detect the occupation status of the assigned space after the restart and indicate the precise total occupancy of the multi-storey car park.

Operators of parking guidance systems

The characteristics of a modern single space detection system are in particular defined by the main users: airports, shopping centres and company car parks. Big private car park operators are considerably rarer customers.

Especially during peak hours’airports need to lead thousands of cars to vacant spaces, without any jams or time loss. Shopping centres are in hard competition. They want to offer their customers maximum comfort meaning a stress free search for a parking space. Many companies have increased their employee numbers considerably over the years. Not only is office space stretched to the limit, employee parking spaces are also reaching their capacity limits. They have to achieve the best possible utilisation of the existing space and thus decide on a single space detection system.

Private parking operators on the other hand are - in regard to the number of spaces under their operation - rarely customers of single space detection systems. The clear assumption is that operators have entered into expensive long term leasing contracts in exclusive inner city locations. Their car parks are very full anyhow and an investment in a technology without a clear cash flow advantage for the leaseholder is questioned.

Communal operators of car parks are establishing themselves as a new and strong customer segment. Their understanding of profitability goes beyond the singular cash flow view of the private operators. Benefits of the overall economy for the community influence the investment decision such as the attractiveness of the inner city, the prosperity of the retail industry and the associated income from commercial tax or the overall goals of reducing traffic jams and environmental emissions.

On top of this single space detection offers further qualitative advantages compared to zone-counting. For instance, time monitoring can show cars that are exceeding the maximum parking time in a free of charge public car park. Unwanted long time parkers can thus be precisely identified. As each space is monitored individually important information can be gathered about the quality of parking areas by measuring how long a car is parked and how often a space is occupied. Every space is clearly marked as vacant (green LED) or occupied (red LED). Spaces for special customer groups such as women, electric-charging pillars or disabled people can be signified by a separate signal colour (such as blue). The occupation of these special spaces are precisely monitored and unlike the zone counting can lead the user group directly to their spaces via a corresponding depiction on the parking guidance displays. If the sensor is equipped with a freely configurable (multicolour) RGB-LED, individual spaces can be given a different colour and allocated to a different user group with the use of a software function. Alternatively, it´s possible to reserve particular spaces for an event and highlight this with the colour of the freely configurable LED. Moreover, special parking areas such as fire rescue paths or emergency exits can be monitored with the sensors.

Implementation and costs of single space detection

As the installation of a single space detection system differs in every car park, making a general cost estimate is difficult. A substantial cost driver is the installation, which is highly dependent on the exact makeup of the car park (ceiling height, number of beams, width of the driving lanes, use of existing cable trays). The design and number of desired parking guidance signs are also an important cost driver. As a rule of thumb for a turnkey overall system (multi-storey with < 400 spaces) costs of between 250 and 300 Euro per space can be expected. It can be recommended to first have a traffic and signage concept drawn up on the basis of the plans for the car park, from which a bill of material can be derived. Along with photos of the car park manufacturers can create a meaningful budgetary offer in a relatively short amount of time. Fundamentally, installation costs can be saved if the system is installed in the context of a new build or renovation of a multi-storey car park.

Next to these onetime installation costs no major operating or maintenance costs arise for the hardware. As single space detection systems do not have any moving parts, the operation is nearly maintenance free. Running costs for the energy consumption of the LED signs and sensors are little. In addition to this are notable savings on ventilation (due to reduced CO2-pollution), savings on lighting (dimming lights on inactive parking areas) and savings through the reduced wear of the car park surface.

Next to the many pros and cons of single space detection from the view of parking operators the citizen is the real beneficiary of a single space based parking guidance system. They will be thankful when the noise and environmental pollution caused by traffic is reduced to a minimum. From the viewpoint of the driver the system has proved itself, when the search for a parking space becomes so simple that the process of parking becomes negligible. In the best case the driver only remembers the actual purpose of the journey after having parked his car without any effort at all.

The author:

Dr. Roland Kraus studied industrial engineering at the Technical University Berlin. He then initially worked as a Management Consultant before taking over as the Director of Worldwide Parking Systems for the Siemens AG. Today Dr. Kraus is the Managing Director of MultiGuide GmbH. MultiGuide develops innovative solutions for parking guidance systems. Further information can be found at

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