How do you play a solo game of Steve Jackson Games' Car Wars?
In my experience....
Solo play of Car Wars breaks down into 4 discrete activities:

Vehicle Design
movement practice
play of automatic opponent scenarios
playing multiple sides
play of paragraph driven scenarios
TurboFire play

Vehicle Design as Solo Play
For me, this was the number one way to waste time with Car Wars. I designed about 50x more vehicles than I ever used in play. And I used a LOT of vehicles in play.
Movement Practice
My friends and I would often draw an obstacle course on a single sheet of paper - usually letter or legal, sometimes 11x17&quot;. And then see how fast we could get a vehicle through. We'd each do this on our own time, and later compare.
I did a lot of this when I first got Boat Wars - the Hovercraft rules needed to be better written. I also did a bunch of this when I first got Truck Stop.
Automated Opponent Scenarios
A few scenarios from Autoduel Quarterly were one vehicle against a prepared course with automated firing rules for the emplaced defenses. (Maniac, in ADQ 1-4, was one of the best.)
Playing Multiple Sides
It was (and still is) a classic wargaming trope to test play games by playing both sides. In a deterministic game, like chess or checkers, it's pointless, but once you add randomization, you can have a very good time playing both sides of a game.
Note that for car wars, this is a prerequisite for solo play of certain modules.
Paragraph Driven Scenarios
There have been several paragraph-driven scenarios released for Car Wars. These are very much in the same mode as the ones for Tunnels and Trolls or The Fantasy Trip; they actually work best when there is a second player, but they work well enough solo, and the intended mode is solo-play.
The best known is Convoy, an SJG product, which was adapted from a GM'd adventure.
Second best, released by Task Force Games, was Hell On Wheels. Far less well known are the two other solo modules from TFG, The Gauntlet and Street Fighter. These three were part of a line called &quot;AutoVentures.&quot;
All four of these presume the player will play both sides in the actual combats, but they also specify the general tactics of the encounters.
The 3 from TFG also include an alternate &quot;Quick Combat System&quot; which made them quite playable without setting up the map and counters. (It also works for some of the encounters in Convoy.)
TurboFire
TurboFire was one of two GM-adventures for Car Wars in the AutoVentures line. It lacked a paragraph mode, but included an abstraction for racing. In and of itself, it was not intended for solo-play... but since it abstracted out thousands of choices into a few die-rolls, it allowed race-dueling to become a solo-play opportunity.
In TurboFire, the players are using the TurboFire racing rules to generate a series of encounters, which then get played out per the restrictions within the module. These generally are short battles, given the harsh restrictions in that module's setting. This combination means that it's pretty easy and quick to resolve each one, and one can fairly easily play both sides, since the tactics are obvious.
I've used this mode with Cars, Big Rigs, and Microplanes.