Adventures in Parking Guidance Learnings From Real-Life Installations

May 6, 2022

Peter Filice

Modern Automated Parking Guidance Systems (APGS) are an innovative and useful technology that can greatly increase parking efficiency and enhance the customer experience. These systems have been available for many years and are pervasive in both new construction and retrofit parking facilities. There are many excellent choices of APGS products and integrators to choose from. This sounds like a recipe for an easy, quick, problem-free APGS installation, right? Perhaps we should not jump quite so quickly to that conclusion before examining the realities of modern APGS installation projects. As the saying goes, “the devil’s in the details”. This article seeks to educate on real-life lessons from field experience in the hope that future APGS projects can avoid or minimize common issues, leading to a smoother and lower cost installation experience and a well-working system.

Given the author’s penchant for music, each major discussion topic is introduced with an appropriately famous song title. 

There’s a Place for Us…

A consideration for all APGS projects is where and how the overhead counting sensors are installed. These sensors -- which may be based on video cameras, ultrasonic sensors, or LIDAR – generally mount over the drive lanes and/or parking stalls and monitor the passage or presence of vehicles in a parking structure. Since the sensors mount in the ceiling area, there are several approaches to placing them. Similarly, the APGS digital signs internal to the garage are usually suspended from the ceiling area.

In all cases, an important consideration for these sensors and signs is to pay close attention to how their mounting height compares with the required clearances in the parking structure. These clearances, sometimes referred to as “Above Finished Floor” (AFF), are determined by the geometries of the parking structure along with local codes and vehicle headroom requirements. Usually, the APGS contractor does not get a say concerning required AFF clearances, but these clearances must be taken carefully into account in the APGS design and construction plans so that vehicles will not hit and damage the APGS sensors or signs. We are aware of one major multi-thousand stall APGS project where many parking sensors had to be shifted higher after construction was done because the AFF specifications were not properly coordinated, and vehicles were striking the sensors. A situation like this one can be very expensive to fix.

There is another issue applicable only in cases of new parking structure construction. That issue is deciding if the power and network conduits and mounting points for APGS sensors and signs will be pre-embedded into the concrete decks before the structure is completed or added later after all concrete construction is done. The former approach can result in a cleaner installation with no exposed conduit and lower conduit/wiring labor costs, but it comes with an important caveat – the exact sensor and signage locations must be determined very early in the garage design cycle. This usually implies that an APGS vendor decision must also be made very early in the process since each vendor has different guidelines for sensor and sign locations. It is not always possible or advisable to require the construction team to make an APGS vendor decision early in the process. All APGS vendors have sensor and signage mounting systems that can be post-installed after the concrete construction is complete, and if these are properly designed and installed, they can be functional, cost-effective, and relatively unobtrusive. The selected approach is a project-dependent decision that must be made with careful consideration and coordination among the garage build team members.

(Accuracy) Against All Odds…

We have stated in previous APGS-related articles and presentations and will repeat here that APGS accuracy is paramount. What good is a guidance system if the parking availability information and counts shown on sensors and signs cannot be relied upon by drivers? 

Well-planned APGS projects should include a system accuracy goal in the design specification, and most leading APGS vendors are aware of and responsive to these goals. However, the “proof of the pudding” comes when the final vendor is selected and when system calibration and testing commence. It is critical that the accuracy criteria are clearly documented and explained in the final contract documents, and it is equally important that a detailed accuracy testing methodology is provided by the vendor and a plan for executing the accuracy test is agreed upon and occurs in an effective and timely manner. 

We have seen several APGS projects where the accuracy criteria were either not well-defined or they were defined but the testing process to verify them was trivial, improperly conducted, or did not occur. This approach is likely to result in a system that is inaccurate, and which ultimately will be ignored by drivers. Another important best practice is to periodically repeat the tests to ensure the system accuracy remains stable. 

Bear in mind that accuracy testing should include all system aspects that have an accuracy characteristic: sensor accuracy, signage accuracy and latency, License Plate Recognition (LPR) capture rates (if the system is LPR-enabled), and overall system accuracy. Furthermore, to be statistically valid, accuracy test results should occur during both busy and idle parking facility times and should gather enough data points so that the confidence in the accuracy calculation is high.

Up on the Roof…

Most above-ground parking structures have a partially or fully sky-exposed top level. This means that in many cases if ceiling mounted APGS counting sensors are used, those sensors have no overhead structure to which they can attach. Even in parking structures with solar canopies, the panel support structure may not cover the entire deck or may not allow ancillary electronic devices to be attached to it. These considerations imply that a different approach must often be used to count the occupancy of the top level, and herein lies several challenges. Not all roof level counting approaches are created equal in terms of functionality, accuracy, and related consequences. Different approaches will be better suited depending upon factors such as if the ramp to the roof level has parking stalls along it, whether the bottom part of that ramp has a ceiling over it, and if the client wants single-space counting of the top deck.

Some designers and vendors assume that installing pavement-embedded inductive loops is the best way to count vehicles headed to or from the roof level. While these can work well if properly designed and installed, they have accuracy limitations and they require tight control of vehicle travel paths. Additionally, these sensors may not be appropriate where roof levels receive snow-cover and removal by plow.  Use of loop sensors can result in a need for installation of bollards or dividers or even can require loss of some parking stalls. There are alternative counting methods such as cameras, ultrasonic, surface mount sensors, and others that may be useful to consider depending on the specific project requirements as they tend to have less limitations.

If pavement-embedded inductive loops are used, it is important that best practices be followed in their design and installation. We have seen projects where loops were improperly sized or positioned or were not calibrated correctly, and therefore were either very inaccurate or useless. A similar problem can occur if the loops are correctly installed but the associated lane-dividing bollards are in the wrong positions. One project had an extreme loop placement problem where the loops were direct embedded into the concrete ramp but then discovered late in the project to be mispositioned relative to the painted ramp lanes – the result of a lack of coordination during the installation process and requiring some last-minute, very expensive workarounds and abandonment of the pre-embedded loops.

Sign, Sign, Everywhere a Sign…

Digital Messaging Signs (DMS), sometimes known as Variable Messaging Signs (VMS), are a critical component of an APGS, as they are the most obvious and sometimes the only “customer facing” component of the system. In recent years, a much richer selection of DMS types and models are available and the choices can become dizzying for owners. The features, colors, resolution, and content that can be supported by various DMS types are wide-ranging – the signs can be simple, or they can be very complex and flexible. One crucially important design principle is that the sign content must be clear, readable, and non-confusing for drivers. Applying this principle can be aeasier said than done on an APGS project, because there are often multiple stakeholders who each have their own idea of what the signs should look like and APGS vendors often have widely varying opinions on this topic. Engaging a skilled parking designer along with an experienced signage/graphics designer can ease the process of choosing the right kind of sign and the appropriate content and avoid issues such as signs with characters and digits that are too small or too dark to read.

It is also important to consider not just today’s requirements but also future requirements when a sign is designed. For example, there was a project on which an above-ground garage was intentionally designed to have additional levels built on top of it at some future date. The owner insisted on installing a level count DMS that only had digit modules for the initially built levels due to cost, but when the extra levels were built that sign had to be replaced with a completely new, larger model. If this sign had originally been designed with a flexible full-matrix display, this would not have been an issue as the display format could have just been modified.

Another factor that APGS project managers often forget to consider is brightness control on APGS signs. Have you ever been driving on a freeway at night and been annoyed by an overly bright LED billboard? Usually this happens because the sign designer or operator did not implement automatic brightness control, which ramps up and down the LED brightness automatically as the ambient light level changes. This same phenomenon can happen with APGS DMS and it can result in either blindingly bright or unreadably dim signs.

Lastly, insist on coordination and clear roles between all those involved in designing, furnishing, and installing APGS DMS. It is common to see issues in projects where, for example, an APGS vendor designs a sign using their standard offerings only to find out later that those offerings do not meet the owner’s corporate graphic or encasement standards. This can result in severe delays in signage and APGS completion.

I’ve Got the Power (and Network)…

It’s important to remember that APGSs are made up of standard electronic devices which require power and networking connections. Usually, these devices use standard power sources (120VAC or low voltage DC) and typical modern networking connections such as TCP/IP over CAT6 wiring. Just like any other electronic device being built into your parking facility, provision must be made to route the needed power and networking connections. This task is often overlooked or oversimplified during the design or bidding phase of APGS projects. It is important to engage skilled electrical and networking design personnel to ensure the proper support for the APGS.

We have seen several projects where the APGS power and networking design did not receive adequate attention, resulting in extra costs, rework, and delays. Sources of power may be too far from where they are needed or unable to provide adequate wattage. Appropriate and safe designs for low voltage wiring that are National Electrical Code (NEC)-compliant may be lacking. There may be misunderstandings about what sort of networking capabilities, locations, and services are required by the APGS. A common misunderstanding related to that last issue is that most modern APGS’s require an external internet connection for calibration, monitoring, support, and Application Program Interfaces (API’s). We have seen several projects where this issue was not understood or the responsibility for who was to provide this internet connection was unclear, resulting in long completion delays.

Also, new standards in how devices are networked and powered are emerging all the time. Recently, some single-space APGS vendors have introduced the ability to power their camera sensor devices using POE++ (extended range Power-over-Ethernet) which can greatly ease the burden and cost of wiring. It is important to ask questions and understand all the options for power and networking. It is equally important to ensure there is clarity concerning who will provide the power and network utilities to avoid the adage about “what happens when we assume”.

Lastly, consider the role that you want your organization’s IT department to play in the APGS project. APGS systems can be designed to have minimal or no connection points to your organization’s IT systems and networks, or they can be designed to integrate fully. Which end of that spectrum you choose usually depends on your organization’s practices and standards, which you should take the time to understand and consider carefully. We have witnessed APGS projects being delayed, stalled, or even cancelled because of a lack of appreciation of the client’s IT or security standards early in the project or a lack of effective engagement of the client’s IT organization. 

Build Me Up, Buttercup…

As with any new construction or retrofit parking project, there are several approaches to design, procurement, installation, and support. There is no single answer – each approach has its pluses and minuses – but it is important to consider the trade-offs and make a clear and informed decision. Three common models are known as design-bid-build, design-build, and vendor/contractor-direct. These three models have differing roles and responsibilities for all parties involved – owner, designer, APGS vendor, builder/installer, and other related trades.

Regardless of the model chosen, there should be an explicit discussion about who will provide the physical installation labor. Most APGS vendors do not have large and geographically distributed installation teams, so they must partner with or subcontract to a local installer or integrator. Be sure this model and the parties involved are clear and compliant with your project’s practices, including the need for local contractor’s licenses, insurance, and compliance with project labor requirements.

It’s also important to remember that an APGS project doesn’t end when installed, tested, and accepted. There is ongoing preventive and corrective maintenance required and the method and responsibility for this maintenance needs to be clearly planned and documented.


APGS installations are seldom as simple as they may seem. The “5 P’s” saying applies – Prior Planning Prevents Poor Performance. With proper education, informed system and feature conceptualization, quality detailed design, solid vendor selection, effective coordination among construction team members, and attentive project management, the chances of a smooth and successful installation increase. Having partnerships in place with knowledgeable and experienced industry consultants, vendors, and installation personnel are an important pre-requisite to keeping your “Adventures in APGS” from becoming a case of “Bad, Bad Dreams”. 

Peter Filice is with Walker Parking Consultants. He can be reached at pfilice@walkerconsultants.com