But only temporarily
but is it?
I thought the temporal improvement would be for everyone who already used the high way (because they will get to their destination a little bit faster). And for the few extra people, who start to use the highway but didn't use it before, the improvment will stay.
the goldberg-steamcrack supports multiplayer. https://gitlab.com/Mr_Goldberg/goldberg_emulator
I only tested it in lan, and it works great. Not sure if it works online, too. You may need hamachi.
And of course: online multiplayer with randos is probably not worth it, as others have pointed out. On one hands it's probably a bitch to set up. On the other cheating is probably rampant.