THE screech of tyres and the scream of warning sounded simultaneously. 'Get in the car]' yelled its well-to-do driver. I had just emerged from a soul record store a mile or so west of New Orleans city centre. 'You're not safe here - get in,' his wife implored.

I got in and we sped off, running a couple of red lights while they lectured me on my foolishness. Even in broad daylight, they said, it was madness to walk in the inner-city fringes surrounding the French Quarter. I thanked them politely, but puzzled privately at such apparent over-reaction.

Last weekend Adrian Strasser was murdered in this sort of place. An Edinburgh schoolteacher on holiday in the city, he was battered to death for his camcorder. New Orleans seems calm and elegant, but much of the city is taut with the imminent prospect of robbery and violence. Once you have experienced it, you sense it everywhere. A few hours after the encounter with my well-meaning rescuers, I experienced it - but emerged unscathed.

It was like taking sweets from a baby. They saw me go to a cash machine, draw out dollars 100 (pounds 66), put it in my pocket and walk off towards my hotel. As soon as I turned off Bourbon Street (the main drag through the French Quarter) the two teenagers robbed me. They need not have bothered to wave the knife in my face, since they knew which pocket the money was in. They simply grabbed it and raced off into the shadows. It was all over in 10 seconds.

What happened next was more scary. I flagged down a car in the vague hope that it could take me to the police. Its occupants were on my side - to an alarming extent. One cursed because he did not have his gun with him and was therefore unable to 'blow them away', while the driver offered to hunt down the villains and run them over. That they seemed ready to kill in revenge for dollars 100 was a chilling indication of the culture of aggression that blights America.

The police said I should count myself lucky to be unhurt (I did). 'It's an evil city,' shrugged the officer who took my statement.

In most parts of the world you can reliably proceed on the basis that the people you encounter are well-intentioned. The anxiety that every traveller feels is fear of the unknown. A certain trepidation is understandable as you approach places such as San Salvador, Kampala and Phnom Penh. After tentatively feeling your way around these cities, you conclude that, although fast-food restaurants might be guarded by men with guns, nothing very nasty is likely to happen to you.

America is especially dangerous because it appears so comprehensible. People speak (approximately) the same language, and there is a veneer of order and respectability that encourages us to believe 'it could never happen to me'. In much of the United States it is extremely unlikely to happen to you. But in the big cities, where the disenfranchised underclass is expanding, guns are cheap and so is life.

It is essential to acquire street wisdom. Talk to the police or the tourist office about where it is safe to walk; one of the duties of staff at the New Orleans Visitor Information Center is to write 'NO' on large chunks of the map they hand out to tourists. Do not carry anything indicating wealth - Mr Strasser's camcorder was a marketable item. A flashy watch or camera marks you as a good target. Do not stop and peer at a map - fix the route in your mind and look purposeful. After dark, stick to well-lit thoroughfares. And if you are attacked, co-operate fully with your assailant.

Tourists are targets everywhere, from Bognor to Bogota, but in most parts of the world, separating visitors from their possessions is done less violently than in the United States. Go to America, but take great care.

(Photograph omitted)