The game. The wonderful thing about Adventures in Comaland is you can use it to explain away incongruences that typically occur in a video game.
Why do you only encounter a limited number of cars when normally the real world would be filled with far more makes and models? Because those are the cars Tanner's subconscious picked up right before he went into the coma. So those are the only cars he can think of while he's out cold.
Restarting missions after failure? Tanner wants to succeed, so his brain resets it back to the original attempt because of his motivation. He doesn't realize that's what's going on but we as players do, so we trigger it.
No one getting run over? Tanner's a cop, he has no interest in hurting innocent people so his mind always ensures everyone is safe if he drives over the sidewalk. They always manage to dive out of the way, even if a real person might not have those reflexes.
Crazy, improbable driving skills? Tanner idealizes himself as a movie-esque wheelman, allowing him to get away with more style and finesse than you could pull off in real life.
An unusual emphasis on cars, with most major plot developments involving them? Tanner's inner focus on driving causes his subconscious to make the world revolve around vehicles.
On a wider extent: This is also why Tanner has access to expensive cars. He has properly memorized some of his favorites or known quite a lot of cars during his time as a detective, which would explain the wide library of cars available. This also explains why his 1970 Dodge Challenger is the last unlockable vehicle but also the cheapest: It's his own car.
This also explains why you have ready access to certain cars that were not available in the U.S. when the game was set (such as the Aston Martin Cygnet and Alfa Romeo MiTo). Tanner has wanted to drive those cars. Alternately, he might have driven those at some point of his life (which we probably didn't see) and wanted to drive them again.
The first few missions are pretty typical cop chase and race missions that don't really make use of Tanner's abilities, such as shifting into oncoming traffic and ramming his enemies head-on (you can, but the game doesn't tell you to). It actually makes perfect sense since Tanner himself having just discovered he has these abilities wouldn't realise and come up with all the various applications shifting has.
Dream!Jericho is a representation of Tanner's subconscious darker thoughts and the "call of the void" wanting him to just give up and die. But at the end of the day he's still part of Tanner, and there are small moments where he's strangely cooperative, such as in the interrogation room where he actually helps clue in Tanner to what the real Jericho is planning, by commenting that building a chemical bomb "doesn't sound like me" and when Tanner comes to the conclusion that the real Jericho is fooling people into believing there's a chemical bomb, Dream!Jericho immediately agrees that it is exactly the sort of thing his real self would do. While he is the main antagonist in Tanner's dreams, he's the part of Tanner that must be overcome in order for Tanner to recover in order to be able to wake up and stop the real Jericho's plan.
