A hoarding is read by someone who is trying not to crash.

Somewhere in the approval meeting, the hoarding gets a second line. Then the founder's photo. Then three bullet points about the new showroom, a phone number, a website, a QR code and the logos of four banks offering finance. On the screen in the conference room it looks thorough. On SG Highway, at six in the evening, it looks like a wall of noise next to a signal.

The problem is the room. Everyone in it is sitting still, reading at leisure, at arm's length. Nobody who will actually see the hoarding is doing any of those things.

The arithmetic of a glance

Sixty kilometres an hour is about seventeen metres a second. Say your hoarding can be read from a hundred and fifty metres away. That gives the driver nine seconds, and they will spend most of those on the bike cutting in from the left. What you actually get is a glance or two, perhaps a second each.

In a second, a person can take in a short line and a name. That is where the seven words come from. It is a rule of thumb, not a law, and we would rather you wrote five than nine. Count the words on your current draft. If the number is in the twenties, you have written a brochure and put it on a pole.

One hoarding, one thing

Before anyone writes a word, decide the one thing the driver should carry away. Usually it is one of these:

• That you exist, here. A new clinic, a new branch, a new showroom two signals ahead.
• That something has changed. Open on Sundays now. Prices cut. A new range in.
• Your name, again. You already have the business and want it remembered.

Pick one. A hoarding that tries to announce the launch, the offer and the brand values at once will announce nothing, because the eye can't decide where to land and lands on the bus in front instead.

If the line needs to be read twice to be understood, it will not be understood. Nobody reads a hoarding twice.

What to cut, in order

When the draft is too long, cut in this order and stop when you reach seven words or fewer:

1. The website and the QR code. Nobody types or scans at sixty. If people need to find you, your name will do that, because they will search for it later.
2. The phone number, unless the number is the brand, or the hoarding is beside a road where traffic stands still.
3. The list. Bullet points on a hoarding are a sign that a brochure was nearby during the meeting.
4. The adjectives. Premium, trusted, world class, best in town. Every hoarding on the road says these, so the eye has learnt to skip them. The same words turn up in the nine words every Indian brand overuses.
5. The second line. Usually the first line was hedging, and the second line explains what the first should have said. Keep the second, delete the first.

What is left is a line, a name and perhaps an arrow. That is enough. A dental clinic opening in Navrangpura needs “Dentist. Open till 9. Next left.” and its name in large letters. It doesn't need the founder's degrees.

The name is half the hoarding

Clever lines have a way of being remembered while the brand behind them is forgotten. The driver repeats the joke at dinner and can't say whose it was. So the name should be big enough to read on its own, and the line should point at it rather than compete with it.

This is where a tagline earns its place, if you have one. A hoarding is one of the few places where there is room for a name and a line and nothing else, which is why we said in do you need a tagline that businesses who advertise this way have the best case for one.

Language and the road

Write in the language of the people driving past, not the people approving the design. On a highway outside a Gujarati town, a Gujarati line will be read faster than an English one, because nobody translates in traffic. We made the longer argument in Gujarati or English. If you need both, put them on two hoardings, not on one.

Test it before you print it

The check costs nothing. Put the design on a phone, hold it at arm's length, look at it for one second and then look away. Ask someone who hasn't seen it to do the same, and to tell you what it was for and whose it was.

If they get both, print it. If they get the joke but not the name, make the name bigger. If they get neither, the line is too long, and you already know what to cut first.

And if you are approving one this week, do the arm's length test in the meeting, with everyone watching. It ends more arguments than any presentation.