Travelling in Mexico is full of mysteries. For a start, why do airport customs officials place the "red/green dilemma" in the hands of chance rather than letting the traveller decide whether or not to declare something?

Arriving passengers collect their luggage and then move through to the customs area. All familiar stuff, so far, until you are asked to press a button connected to a large traffic light that has no amber, just red and green. This randomly decides whether or not your luggage is to be searched. The red light spells the danger of having your underwear inspected. At a ratio of about five green to one red, that means 60 people on a typical charter flight to Cancun can expect the customs men (I have yet to see a woman in this particular role) to have a good rummage before being allowed through.

Next enigma: why don't Mexican bus drivers fill up with diesel before they fill up with passengers? Typically, five minutes after setting off for a long journey with a full payload, the driver and his conductor will stop at a filling station to replenish the tank with diesel and, furthermore, engage in all the usual peripheral activities: buying snacks and drinks, phoning the girlfriend and visiting the caballeros, while 50 passengers simmer silently in the noonday heat.

Finally, why, last Saturday afternoon, did three gentlemen in a red car drive past me on the road to Villahermosa airport; then turn, drive back and offer me a lift?

To set the scene: Graham Greene located The Power and the Glory in Villahermosa, whose name translates as "beautiful town". Compared with other settings for the master storyteller's works – such as Asuncion in Paraguay or Brighton in Sussex – the heart of this scruffy conurbation has few redeeming features visible to tourists at ground level. I marched dutifully up the 212 steps to the top of the new mirador, astride the turgid Grijalva river, to see if the city looked any better; in fact, it looked worse because you could see more of it in one go.

I plodded down to the foot of the tower, flagged down a camper van to take me to Highway 185, then sprinted to catch a Palenque bus that, for five pesos (10p), would take me to the airport turn-off.

In almost all circumstances I would rather hitch than hike. But when the bus dropped me at the aeropuerto junction, I decided that the couple of kilometres to the terminal was too uncomfortably short a distance to thumb a ride. So I trudged on in "the blazing Mexican sun and the bleaching dust " with which Greene opens his novel.

Travel can demonstrate an agreeable sense of balance. On this page last week, I reported successfully thumbing down a van in south-west France, only to see my pal Mick take the single available seat, leaving me to wait for the bus. Last Saturday the compensation arrived: a lift for which I didn't even have to bother hitching.

You might question the wisdom of accepting an unsolicited ride with three strangers, but, so far, presuming the best intentions of people when a stranger in their land has worked for me. In the two minutes it took to reach the terminal, I learnt that my benefactors spoke perfect English, and that two were Mexican and the third Brazilian. But I never discovered why they chose to disrupt their journey to help possibly the sweatiest backpacker in Mexico. They delivered me safely to the air-conditioned haven, and in the best of spirits to board the plane of the future (see box, below) for a flight to Cancú*.

Why, though, was I heading for the airport at all, when Mexico has such excellent long-distance buses to reach the Caribbean resort? For £27, I could have covered the 500-odd miles to Cancú* in under 12 hours aboard an ADO coach. But I was suffering "tope-fatigue": too many bumps in the road.

On one level – if "level" is a suitable word to use in the context of speed humps – the topes that corrugate the Mexican road network are simple and effective safety devices. At the approach to villages on main roads in Britain, you see 30 or 40mph signs, Mexico has more concrete impediments to excessive speed. Sometimes, a series of blunt protrusions merely provides a rumbling reminder to slow down; usually, though, a mini-Hadrian of a barrier stretches across the highway, requiring vehicles to slow almost to a halt or risk wrecking suspension and occupants' heads.

On another level, topes form an essential part of the economy. At villages, cold water or fresh melon is on offer from children hovering by the humps, while in cities, newspaper vendors risk their lives to dispense news to motorists. But after a week of frequent sharp braking followed by a sudden upthrust, then bumping down to earth and accelerating rapidly towards the next obstacle, I had had enough of G-forces usually associated with astronaut training.

For those who rent cars, the bumps are even more of a nuisance. A fellow-traveller who had hired a car in Mexico ruefully told me that topes are a utopia for unscrupulous types: "They allow people to rob you as you stop to work out how to negotiate the tope; and permit car-hire companies to rip you off when you break a bit off the front of their Ford Tapir."

Flying into the future

The aircraft, registration code XA-TIC, is 10 years old. It belongs to Aeromar, a brand that I would not necessarily have picked to describe a land-based Mexican airline (the name means air-sea). Aeromar has a fleet of ATR turbo-prop aircraft, built by a Franco-Italian combine, and assembled – like many Airbus jets – in Toulouse in south-west France.

This one (right) is an ATR42, the original model, holding 50 people; the "stretched" version, the ATR72, carries 70.

Aeromar claims to be "the executive airline of Mexico", but I have yet to fly on a less business-oriented flight. Apart from the perspiring Englishman in seat 11A (pictured above), everyone else is in family groups, with fathers enthusiastically tucking in to the unlimited complimentary tequila while their spouses and children guzzle peanuts. It helps to keep us occupied, because this is a long flight: it will take us two hours airborne to cover the 500 miles to Mexico's leading resort.

So, why should this be the aircraft of the future, when much faster jet planes are standard? Because every time the price of oil rises, or concern for the planet increases, the future for turbo-prop aircraft looks brighter. On a 250-mile journey, the ATR42 consumes 40 per cent less fuel than jets of the same size, and, says the company, its planes "emit 30 to 50 per cent less greenhouse gases".

In the past 20 years, ATR has delivered 727 aircraft, which are flown by 134 airlines in 79 countries. While the Boeing 737 and Airbus A320 are the jet workhorses for low-cost aviation, the ATR turbo-prop fills a gap on routes that would not be viable by jet. Regional jets are much more complex machines, they cost more to buy and demand a much more expensive maintenance regime. In contrast, the ATR42 is simple, robust and quiet.

A head-count reveals that only 38 people want to fly from Villahermosa to Cancú* this afternoon. Given the way that the airports consume time – everything from arriving in good time at the departure terminal to waiting for baggage on arrival – the extra hour or so on a journey is inconsequential; and for many shorter hops, there is little discernable difference between jet and prop flight times.

My one complaint: the fare, which suggests Aeromar is not sharing the savings with me. Booking well in advance, I paid £140 for the flight. Perhaps, then, I will take up the stewardess's kind offer of a second tequila, and toast the trio who rescued me from the roasting roadside.