Bob, a high school senior who is well over six feet tall and weighs in at 200 -plus pounds, usually does pretty much as he pleases in any crowd. But after a party in a Skokie home the other night, his student friends decided he'd been drinking too much to drive home safely. Four of them, as he told it, simply ''jumped'' him and took his car keys. Slightly aghast at the intensity of the concern but facing little choice, he spent the night at the host's house.
That kind of up-front concern about fellow students who drink and drive is increasingly common these days at teen-age parties in this Chicago suburb. One major reason: establishment last year of an active chapter here at Niles North High School of Students Against Drunk Driving (SADD). The first such chapter in Illinois, it is now one of more than 30 in the state and 6,000 nationwide.
The operating theory is that greater awareness of the problem on the part of teen-agers and strong pressure from peers rather than adults to do more about it are key weapons in the nationwide grass-roots effort to stop the mix of drinking and driving.
That combination is the leading cause of death among teens. Studies show that 16- to 24-year-olds, though only 22 percent of all drivers, cause 44 percent of all nighttime alcohol-related crashes.
Martin Lev, an outgoing and athletic-looking senior at Niles North who is president of the SADD chapter there, says he has been somewhat surprised to see how receptive his fellow students are to trying to find ways to lessen the problem and act on it.
Instead of being shut out of more conversations and parties because of his involvement with SADD, he says he has found himself more popular and included in more parties than before.''I expected to be sheltered out and somewhat harassed but it hasn't happened. And even if people don't honor what I say, they respect it. Believe it or not, no one's laughing at SADD.''
Indeed, the SADD chapter at Niles North began with five officers but now includes more than 10 percent of the student body. ''We've got the greasers, the jocks, the preppies and at least one alcoholic,'' says David Schusteff, director of practical arts at the school and overseer of SADD activities there.
Chapter activities range from hearing visiting speakers and having informal chats in the cafeteria with other students to an organized program of monitoring alcohol-related traffic cases in a nearby court. Some 44 trained students take turns in teams, accompanied by a parent for transport and supervision, sitting in on the cases and keeping careful statistical records.
''When you do that and hear the graphic details, you're not an outsider anymore - you're actually in the case,'' says Marty, who insists he has been interested in traffic safety since he was a small boy and intends to head into traffic management - perhaps followed by a US Senate run - as a career.
In Marty's view, SADD's very existence has had a major impact on the student body. Most notably, he says, the attitude at parties has changed. Students often now routinely stay overnight and drive home the next day or decide in advance who won't drink and will drive the others home.
''There's always a choice,'' insists Mr. Schusteff, who happens to live near a busy highway in another suburb which makes the newspapers consistently for the high number of drunk driving accidents there. ''You can walk, take a cab, or stay where you are. The only wrong choice is driving.''
And increased concern about the well-publicized problem has given an easy way out to students who drink only because their friends do.
''More people are saying, 'No' - that they don't want to drink,''says Marty.
''As SADD members they can be the ride home,'' Mr. Schusteragrees.
Many members of SADD also sign contracts with their parents, agreeing that neither party will drive after drinking or ride with others who have been drinking. Under it, a son or daughter who has been drinking or would otherwise ride with someone else who has is free to request safe transportation home with no questions asked until later.
The legal drinking age in Illinois, as in 19 other states now, is 21. Thus much of the pervasive drinking that goes on among high school students here - which Marty says may even have gone up recently in response to an effective and widespread crackdown on drugs at Niles North - is illegal.
Yet Marty, who says he occasionally drinks himself, stresses that he and other SADD members are making no moral judgment on whether or not students ought to drink. ''Preaching'' against it, in his view, would have little effect and could easily keep students from hearing SADD's main message: drinking and driving must never be mixed.