Same paint, same wheelchair symbol on the ground, same line in the planning approval. Almost no two accessible bays actually work the same way. One ends in a kerb cut onto a level pavement. The next has a hundred millimetre lip on every side, or an access aisle that has been parked across by a Range Rover, or lighting that switches off at six. The symbol on the ground tells you almost none of that.
Below is what actually decides whether a bay is going to work, in roughly the order it tends to bite.
Bay width
Width is the number we start with. A standard British bay is about 2.4 metres across. An accessible bay should be 3.6. That extra 1.2 metres is the entire reason the bay exists. Without it you cannot get a side ramp out properly, a sliding door will not open fully, and a passenger transfer has nowhere to go.
You would think this would be enforced consistently. It is not. Multi-storeys built before the eighties were laid out for cars that no longer exist, and a lot of them still have what they had then. We have measured 1960s decks with "accessible" bays at 2.2 metres, where a Vauxhall Astra's mirrors do not clear and a sliding door opens about halfway. The paint says yes. The tape measure says no.
The access aisle
The hatched stripe next to or between accessible bays. It is not extra parking. It is the bay. That zone is where the ramp lands, where there is room to clear the door, where someone helping with a transfer can stand without being in the next bay along. Without it, a 3.6 metre bay collapses back into a 2.4 metre bay.
A properly designed aisle is at least 1.2 metres wide and runs the full length of the parking space. In car parks where the lines have faded, you can almost guarantee that someone has decided the hatching is a free space and parked half over it. By the time you arrive the bay is unusable, and there is nothing much to do short of photographing the offender and emailing the operator.
Getting from the bay to the pavement
You have parked. Now there is the bit between the car and wherever you actually need to be.
The first thing is whether there is a dropped kerb at the head of the bay onto a pavement that goes somewhere. A surprising number of accessible bays have been painted in where they fit on the deck, not where they connect to anywhere onward. A hundred millimetre kerb between the bay and the only useful pavement rules out the destination, the building, and the day you were planning to have. If you have never thought about how often this happens, the answer is a lot.
Then the gradient. Approved Document M of the UK Building Regs sets the proper figures, and quite a lot of "accessible" routes do not meet them. We have logged plenty of one-in-eight slopes labelled accessible, when one in twelve is the upper end of what is workable, and even that is hard work.
Surface
Surface matters more than people tend to think it will, particularly for ambulatory disabled people, anyone walking with sticks or a frame, and anyone using smaller mobility aids. The bay can be the right width, in the right place, on the right route, and still be a no-go because of what is under your feet or wheels.
Tarmac, smooth and recent, is the best surface to land on. Concrete is generally fine. Block paving and setts are the in-between cases, where individual stones are level enough but the joins between them catch caster wheels. Cobbles are genuinely difficult for many wheelchair users, and a lot of medieval European city centres are entirely cobbled, so the city's "accessible" bay can sit right at the edge of an unusable surface. Gravel and grass are not really workable for almost any mobility equipment.
Lighting
A bay that is perfect at two in the afternoon can be useless by seven. If the nearest streetlight is out and the kerb cut is somewhere in the dark behind a parked van, that is the trip. Theatre runs, hospital follow-ups, late winter afternoons, any of those.
What you actually need is direct light over the bay itself, not somewhere across the car park. And the route from the bay to the door has to stay lit and level the whole way. The bit people forget is the gap. A lit car park and a lit destination, with forty metres of unlit pavement in between, is where the trip comes apart.
Distance to the door
The closest bay is not always the best bay. Six metres from the entrance is irrelevant if there are five steps in between. Thirty metres further out, with a level path, is almost always better.
Distance is one number. The obstacle count is the other. Kerbs, gates, awkward thresholds, doors with the wrong kind of handle, the bit where the pavement gives up halfway across. The whole route has to work, end to end.
Safety
A few things people skip past when they should not.
A multi-storey corner with no windows or cameras facing it is not somewhere you want to be at half past ten at night, transferring out of a passenger seat. CCTV does not make a bay safe, but it does change the behaviour around it. And faded bay markings are the slow-burn problem. They let other drivers half park over the aisle, which means that by the time you come back the bay is no longer a bay.
What changes through the day
The same parking space, twice a day, different planet. Loading bay rules that activate at four. Markets at the weekend. Resident-only enforcement at six. Lighting off at midnight. If you are going somewhere regularly, the version of the bay you scoped on a quiet Wednesday lunchtime is not the version you will meet on a Friday evening.
What the symbol tells you, and what it does not
A wheelchair symbol painted on the ground is a planning intent. The council, the operator or the developer meant this space to be accessible. The symbol says nothing about whether the bay actually is, on the day you turn up, with the equipment you are bringing.
That gap is the whole point of Close to the Door. Every bay in the app has the actual numbers, the bay width, the kerb cuts, the surface, the lighting, checked by Disabled drivers and passengers who have used it. It is not perfect. It is the difference between a symbol and a bay.