70a/80s sci-fi: scientists trying to send message into the past to avert catastrophe

I’m looking for a 70s/ early 80s movie where a couple of scientists try to avert some desaster by sending a message to themselves back in time (an hour? A day?). They succeed.
I vaguely remember a scene that happens at the beginning and the end of the movie, where one of the protagonists rides on a highway (desert?) on a motorcycle, you see the road stretch to the horizon. In one variant, a bomb goes off far in the distance. From my memory fragments, I’d assume the driver of that motorcycle hurries to the lab, they fix their experiment and manage to send the message (I think the lab is underground and collapses right when sending), receive it, inform authorities, danger averted, something like that.
Overall “grit” of the movie, hairstyle, pants, stuff like that, from the vague pictures I have in my head, reminds me of movies like “future world”. Ideas? Thank you for your time!