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Buyer's guide
How to choose a parking guidance system
Counting, ultrasonic or camera detection — the honest comparison, written by the people who install all three and then service them for the next decade. Including when the answer is that you do not need one.
Start with the complaint, not the technology
Almost every guidance project starts with a symptom. The symptom tells you which system you need, and specifying past it is the most common way to overspend on a garage.
- “The garage fills and nobody knows”
- You need counts at the street and the ramp. Level counting. Cheapest per bay by a wide margin.
- “Drivers circle a deck that has room”
- They cannot see the open bay. Per-space detection. Counting will not fix this.
- “Visitors cannot find their car”
- That is a tracking problem, not a guidance one. LPR with find-my-car.
- “Accessible bays are always misused”
- Per-space detection with bay classes and alerting. Counting cannot see bay type.
- “We do not know what we actually have”
- Start with counting and reporting for a season. Buy detection once the data says where the problem is.
The three detection methods, compared
There is no best sensor. There is a best sensor for a particular deck, and the trade-offs are consistent enough to put in a table.
| Level counting | Ultrasonic per bay | Camera per bay group | |
|---|---|---|---|
| Answers | Which floor has room | Which space is open | Which space is open, and what is in it |
| Devices per 100 bays | 2–4 lane detectors | 100 sensors + indicators | ~17 heads (6 bays each) |
| Relative cost per bay | Lowest | Highest device count | Higher per device, fewer devices |
| Cabling burden | Minimal — lanes only | High, unless wireless battery units | Moderate — one run per head |
| Low light and headlights | Unaffected | Unaffected | Needs adequate light or IR |
| Drift over time | Yes — needs recalibration | No — each bay reports itself | No, but aim and lens cleanliness matter |
| Gives you anything else | Occupancy trend only | Dwell per bay | Dwell, plate reads, misuse alerts, security review |
| Best on | Commuter and staff decks | Clean indoor decks, retrofit with wireless | Visitor, patient and mixed-use levels |
Most garages over roughly 400 bays end up mixed: counting where drivers know the building, per-space where they do not.
Sizing tool
What would this cost to run, and what does it get back?
Order-of-magnitude sizing, not a quote. Adjust the garage and see what changes.
Hours wasted assumes the stated search time on every arrival. Recovered capacity assumes guidance removes two thirds of it — the conservative end of published studies. Your figures will differ; we measure them on site.
Seven questions worth asking any vendor
- What happens when a sensor fails? A bay must report unknown, never open. If a fault sends drivers to a taken space, the signage loses credibility and people stop reading it.
- Who owns the data? Occupancy and plate reads are your operating record. Confirm you can export them and that they survive the end of the contract.
- How does it recalibrate? Counting systems drift. Ask what the routine is and whether it happens without a truck roll.
- What is the failure rate by device, in the field? Not the datasheet MTBF — what their own service records show.
- Can it integrate with the access system we already have? If the answer requires replacing your PARCS, that is a much bigger project than you were quoted.
- Who fixes it, and how fast? The installer and the servicer are often different companies. Find out before you sign, not at the first fault.
- What does year six look like? Parts availability, firmware support and the cost of a partial refresh matter more than the install price.
If a vendor cannot answer the last three from their own records, they are a reseller rather than a servicer. That distinction shows up years later, not on the quote.