Airport parking, taxi, train or a lift: when does driving win?

The short answer: when driving wins

The rule points a direction, it is not a formula. Check five conditions:

• Two or more of you are travelling.
• Departure or return falls outside the hours services run.
• The stay is longer than a long weekend.
• You come back with children, a pushchair or sports gear.
• The hour of the return is uncertain.

Three ticks are enough: you are driving, and the rest of this text only explains why. With one tick or none, read on closely, because rail or a taxi usually takes it.

How many of you are going

The number of passengers turns the ranking over faster than anything else. Alone with a backpack you keep every option open; as a family of four, half of them drop out while you are still counting.

In a car the headcount changes almost nothing. A space costs the same however many people climb out of it, and the ride to the terminal is usually part of the parking price. The exception is a surcharge for passengers above four or five in the shuttle: some lots have it in their price list, and it shows before you pay.

On the railway it is the other way round. Every extra person is another ticket in each direction. Children have their own fares, but they still count, and with a larger family the total climbs in a way you never notice when planning a trip on your own.

A taxi charges for the run, so four people travel for what two would pay, as long as everyone fits with the bags. At five you are ordering a larger vehicle, and that is a different service with a different price.

The hour you fly and the hour you land

Timetables are the one part of this puzzle that does not negotiate. A dawn departure and a late evening landing cut options away before you have counted anything at all.

At night the train either does not run or runs so rarely that the first morning service gets you there after check-in has closed. Night buses exist, but not everywhere and not from every district.

A taxi goes at any hour, it only has to be booked ahead, and before dawn there are fewer drivers around than people who want one. Ordering the evening before settles it, as long as the driver reaches your door.

Here the car has an advantage nothing can take away. It stands where you left it and waits exactly as long as it has to. A shifted flight changes nothing in its plans.

The way back is harder than the way out, because the landing hour is not yours to know in advance. You build the departure from a calendar and receive the return from an airline, and every hour of slippage removes one more item from the list of options.

Bags, children and child seats

Luggage rarely enters the comparison, and it overturns one as reliably as the arithmetic does. Two big suitcases, a pushchair and a child seat look one way in a boot, another way in a carriage and another way again in somebody else's car.

Your own child seat rides in your own car where it always sits, and nobody has to refit it. In a taxi you order one separately, and not every operator keeps them. On a train the problem disappears, except that the seat has to be either carried or left at home.

Suitcases on a train are really a question of changes and stairs. One direct service from the station to the terminal is comfort; two changes with a pushchair and three pieces of luggage make a different journey from the one in the timetable.

In a car you pack once, at home, and unpack at the lot. With a shuttle there is one handover of bags, with meet & greet there is none at all, because you step out right by the terminal.

What drives the cost of each option

Comparing ways to reach the airport goes wrong the moment you reduce all of them to one number. Each option grows from a different thing, and naming that thing is what turns the comparison into an answer.

Parking grows with the length of the trip. You pay for the days the car stands there, and the drive itself changes nothing: the same lot works out one way for a weekend and quite another way for three weeks off.

A taxi or a booked car works the other way round. It is two separate runs, out and back, and whether you return after three days or after a month makes no difference to either of them. A night run may be priced higher than a daytime one, but it is still a run, not a subscription.

Trains and coaches grow with the number of passengers. Everybody needs a ticket, so one traveller pays once and a family pays as many times as it has heads. On top of that comes getting to the station, which almost nobody counts.

A lift from a friend appears on no price list, but it has a cost: somebody else drives to the airport and back, twice, at hours they did not choose for themselves. Worth naming before you file it under free.

The table gathers the above into a single view. It carries no rates, because a rate depends on your dates, your city and your headcount. It carries directions, and those do not change from season to season.

When driving does not win

Rail or a taxi wins when you travel alone, come back within a few days and have a direct connection at a civilised hour. Then a car standing there for a whole week is simply a dearer way of doing the same thing.

When the conditions split down the middle, the return decides it. A known landing hour and a timetable still running keep the choice open; an uncertain hour closes it on the car, because only the car waits without charging for another run.

Do the last step on real data all the same. Enter the true date and hour of departure and of return, add the headcount, and set the result against the price of tickets or a run. The direction tells you where to look, and the sums on your own dates decide.