WIRELESS NWAVE CAR COUNTING SYSTEM

A wireless alternative to expensive and restrictive wired car counter systems. Track available spaces with minimal investment

How does the car counting system work?

Unlike per-space sensor that need to be installed in the individual parking spaces, car counter sensor are installed in entry and exit lanes. Knowing the total number of spaces in the controlled area, the system simply subtracts number of cars counted at the entry (cars in) and adds the number of cars counted at the exit (cars out) to calculate the number of available spaces.

Traditional Wired Car Counter Systems vs. Wireless Nwave Car Counting System

Traditional car parking counting systems typically involve two types of systems – in-ground induction loops or various kinds of wired counting hardware solutions installed in the vehicles’ entrance and exit paths (these may be camera-based, radar/LIDAR-based, etc.)

Induction Loop Solution

Camera-Based Solution

Induction loop car counting solution is the oldest and the simplest one, but lacks accuracy vs. other modern solutions and, most importantly, requires installing induction wires into the pavement, which makes it expensive to install and maintain. Camera-based and other wired systems are, generally, more accurate, but all share one feature in common – they all require access to some mounting physical infrastructure and to electricity at each counting point, making these solutions particularly expensive where these are hard or expensive to provide, including outdoor applications.

Unlike traditional wired systems, Nwave car counting systems relies on wireless Nwave sensors, placed on the ground in the vehicle’s entrance and exit paths. As a result, this car park counting solution does not involve drilling the pavement, unlike inductions loops, and does not need access to electricity or any special mounting infrastructure at the counting location, allowing installation and maintenance of this solution at a fraction of the cost of the traditional wired solutions – for indoor/garage applications but, in particular, for outdoor applications.

Nwave Vehicle Counting Sensor Solution

Compared to per-space sensor solutions, 2-5 car counter sensors in a car counting mode sometimes can replace around 200-900 per-spaces sensors.

But, as always, there are some trade-offs!

Cost vs. Accuracy

There are a few fundamental factors that make car counting systems inherently less accurate than per-space sensors.

Detection Timing

The per space sensor has all the time to detect the car. Once a vehicle has parked, it can also verify its detection with multiple repeated measurements and then check the vehicle’s presence every few seconds. The car counter often has just a couple of seconds to detect a passing vehicle. And sometimes it can be one long vehicle and sometimes – two short tailgating cars.

Error Accumulation

No detection is 100% accurate, a per space sensor can also miss a car but there is an important difference in the error treatment mechanics between per space and car counter sensors. In every car counting system (including induction loops, wired solutions, etc.) an absolute occupancy error is proportional to the total turnover (number of cars counted) and this error builds up over time, the so-called “error accumulation” or “error creep” phenomenon. In the case of per space sensors, since each sensor resets itself every time a parking event takes place – it is always a direct measure of the number of spaces/sensors in the lot. Let’s consider an example where we have a 99.5% accurate system of two types installed in the lot of 100 spaces and a daily turnover of 100 cars. In one month, we will have a 3,000 vehicles turnover and a 0.5% error gets us an expected 15 spaces / 15% error for a 100 spaces lot. And in two months the error will double. In most cases, it is only a question of time when the counting error will creep to an unacceptable level. Per space system with no error accumulation, on the other hand, will remain, 99.5% accurate. In the same case of a 100-space facility, it will always remain 99.5% accurate, meaning a maximum error of 0.5 vehicles/spaces at any given time.

When does the car counting system work well?

Based on our experience a combination of two factors makes a good case for car counters as a lower cost and acceptable accuracy alternative for per space sensors.

Well Defined One-Way Entry and Exit Lanes

Broad bi-directional entries and exits are more prone to counting errors. Even a little accuracy reduction from 99.5% to 98%, that may take place in such an environment, can result in an unacceptable 15%+ error in just one week of operation. Narrow, well-defined, one-way, straight entry and exit are much easy to operate with high counting accuracy which can maintain a reasonable total availability estimate within a week even in the case of a high turnover lot.

Below are two examples of “bad” and “good” counting configurations. On the left – an example of data flow for a counting solution that has an inherent accuracy deficiency, leading to error accumulation over time. Such deficiency could be due to limitations of a counting hardware, or, in case of using a ground-based sensor, due to broad entries/exits where a vehicle may missing a counting sensor while entering or exiting the facility. On the right – an example of a “good” counting solution deployment with no error accumulation.

“Poor” Counting solution – Error Accumulation

“Good” Counting solution – No Error Accumulation

Situations when “natural” design of ingress and egress lanes of a parking facility are not sufficiently narrow or well-defined can be corrected by installing mobile barriers or traffic flow dividers – as per the two examples below. Such barriers provide a quick and inexpensive fix to ensure accuracy of a counting solution, while remaining relatively “low key” and unobstructive for the drivers and general public. Such mobile dividers can also be promptly removed to allow access for larger vehicles/trucks, such as authorized utility or maintenance vehicles, into the facility.

Nwave-wireless-car-counting-system

Examples of mobile barriers and traffic dividers application to remedy wide and bi-directional entrances for counting applications

Regular Off-Peak Hours

Due to accumulating nature of counting errors, the real occupancy for all car park counting systems needs to be reset periodically. With a parking lot that has clear off-peak hours, e.g. employee parking on Sunday night, the occupancy can be reset automatically which helps to maintain a good accuracy with minimal effort. 24/7 operated lots with no clear off-peak hours, e.g. airport parking, on the other hand, will require periodic manual counting to minimize accumulated counting error.

Flexibility to Build Hybrid Solutions

The same physical Nwave sensor hardware is used both for per-space and counting applications. This means Nwave sensors allow to build highly flexible “hybrid” solutions for e.g. large surface parking lots or garages. In such hybrid solutions, car counter sensors can be used to provide overall vehicle count for a particular facility, while per-space sensors can add additional data granularity for high-value spaces, such as EV, disabled, visitor, carpool, etc. spaces. Since both sensor solutions work under common sensor-gateway coverage, such approach allows to create highly flexible wireless solutions for projects with various requirements to accuracy, data granularity and price level.

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Car Counting System