True Gripes: Naked - and dead?: Summer bikers who bare too much

Many are the pleasant things about London in summer. Each year they recur: the Isley Brothers' 'Summer Breeze through open car windows; the black boys' fluorescent string vests; the sound of the neighbours washing up drifting across the street; the smell of hot plane tree. And, just as regular, come the idiot motorcyclists in sandals with girlfriends bare-legged on the pillion.

These are not on the whole regular riders. They are the kind who keep the bike tucked under canvas all winter. They think leather is for keeping warm and don't ride when it's cold. When the sun comes out, so do their naked elbows and their scrawny white knees, whizzing round town as if the bike were a fairground ride and the city an adventure playground paved in nice bouncy cork tiling.

But the city is tarmac and York stone and iron railings and the bike is a hard metal machine around a hot metal engine. Riders ought to know the relationship between tarmac, hot metal and naked flesh. Many do, and put a layer or two of denim or leather between their flesh and the outside world. Of course it doesn't feel quite so gorgeous as summer breeze wafting over sunkissed skin, but even a little imagination tells you what a hot exhaust pipe feels like welded to your calf.

Of course it's groovy to go on a bike. Of course you want to show off and hang loose and flash your tattoos and get the wind in your hair making like Marlon Brando in the sun. As a biker temporarily reduced to a car, I flinch every time I see a naked hand clutching a handlebar. All those delicate bones, those clever muscles, the fine machinery of the human hand, or elbow, or ankle, laid bare to such bloody mayhem so easily caused and so easily, much of it, avoided. I find it frightening that people make themselves so vulnerable, and allow others, who often don't know any better, to be so vulnerable too. And it's me - the car driver - who is most likely to damage them. When a biker overtakes me on the inside I want to know that at least he's got boots on.

We riders make up our own minds: we choose whether to behave like immortals. The people I really fear for are the pillions: those who believe (and are allowed to believe) that because there's a spare helmet they can safely go on the back.

And on the back they go; half-clad women in little skirts and sandals, boys in vests and espadrilles, naked ankles centimetres from hot exhaust pipes and their whole unprotected self the tiniest nudge from really nasty damage.

Apart from the requirement to wear helmets, bikers are in law responsible for their own protection. This is right - not least because some of the 'protective' apparatus law-makers have tried to introduce has been dangerous (leg-guards, for example, which made it impossible to jump free in an accident). What makes a biker safe is personal. Full-face helmets are, in theory, safer: I can't abide them because I feel cut off from traffic, less alert and hence less safe. But when it comes to pillions, particularly summer weekend pillions, the rider must take responsibility for them, too.

Car drivers are legally responsible for their passengers wearing seatbelts. Riders might at least encourage pillions to put something on their feet.