JOHN J. PYNE was five minutes from his Vienna home when his car broke down on I-66 Tuesday. He knew what to do once he pulled onto the shoulder and stopped: Call for a tow truck, call his wife, stay put in the car. But what was once a shoulder there is now an exit/deceleration lane to the Capital Beltway. Mr. Pyne was killed when his car was hit by a tractor-trailer using the lane. On deadly I-66, a shoulder sometimes isn't a shoulder; it turns into another lane of traffic during rush hours. At other times most of it looks like and is used as shoulder--except near exits, where vehicles can use the lanes to leave the highway. If that is not clear, neither are many drivers out there on this extraordinarily busy strip.

Shoulders are for breakdowns. Exit lanes and rush-hour lanes are for fast-moving vehicles. Mixing these uses is lethal. Maybe some everyday commuters know the drill, understand the signs and have the skills to pull a limping vehicle into a place where they can get out, hop over a railing and stay in the grass until rescued. But how many first-time or occasional users of these highway lanes know that here, the old sound advice about parking on the shoulder and staying behind the wheel is bad?

In the wake of this latest death, the regional AAA chapter chucked that advice, noting that mixed use of shoulders has made all shoulders dangerous: Including Mr. Pyne, five people have died in their vehicles in the past month while stopped on area interstate roadside shoulders. AAA is now urging people who must use shoulder lanes to stand as far off the road as they can, behind guard rails or barriers where possible.

The conversion of shoulders into travel lanes should be stopped. If more lanes are needed, as they clearly are in congested Northern Virginia, more lanes have to be added. Virginia highway officials say the deceleration lanes at exits were created as a safety move, that while this has meant taking away some shoulder space in areas where there isn't enough room for both, it's a "trade-off." But not a good one. Perhaps more emergency pull-over areas off the roads could be created. But a shoulder shouldn't double as a traffic lane.