Actually you don't. A well known attack against trucking is to suspend a cinder block from an overpass, just high enough for the cars to miss it but not the trucks. People put them up in the middle of the night and are miles away before an incident.

Dropping caltrops on a secondary road at night would also work. Rigging a drone to drop chaff on a freeway, etc, would also get the perpetrator physically away from the action. Really, with some creativity, surprisingly crude attacks can shut down a road with minimal exposure of the perp.

A decade ago, the Beltway Sniper terrorized my neighborhood for two weeks. It turned out to be a teenage boy and a certifiably insane adult with some military training. A similar attack by someone who actually knew what they were doing and who wasn't addled would have been very, very difficult to catch. Much less if the attack were, say, from wooded roadsides that overlooked interstates.

>There's another aspect to it: sure you could disrupt traffic with all the means you cited, but you had to be there physically, and you'd run the very likely risk of being caught and beaten up by angry drivers

Dropping a handful of nails over an overpass is unlikely to be noticed, much less attract retaliation from the victims