For reasons that will be clear in a month (having to do with another Henry Koster/James Stewart collaboration), I would personally love to see No Highway get a Twilight Time release at some point. Among other things, it features a very good performance by James Stewart, and a good supporting performance by Marlene Dietrich.
I agree with Robert Harris - it's more of a whistleblower story. And it builds up an amazing head of tension before it's done. It's a movie where you live in certainty that something horrible is about to happen, and it's only a question of when.
A drama teacher of mine once taught us what I think is the Hitchcockian definition of suspense and terror:
One situation is a guy walks into your classroom and says "I've put a bomb in the desk. It will go off in five minutes unless you can figure out a way to disarm it or get out." That's suspense.
The other situation is a guy walks into your class room and says "I've put a bomb in the desk. It will go off soon but I'm not telling you when." That's terror.
I always liked that as a situational definition - and it definitely applies to No Highway.
With the Poseidon Adventure, part of the fun is that you have the big disaster happening early on, and then you have a series of mini disasters that befall our heroes as they try to find their way out of the mess. It's still fresh in The Poseidon Adventure. With a later movie like When Time Ran Out, the devices have become so predictable that as soon as you see the river of molten lava, you immediately know that SOMEBODY is about to fall into the darn thing...