During the allowance* turn, the number of cubes of the same color that may be purchased is limited.
(*The "allowance turn" is the one described by the rules as the first turn after driver selection which gives each player an “allowance” based on their starting position to purchase cubes before the race begins.)
This tables gives the limit.
2 no limit
After the allowance turn, there are no restrictions.
In games with 3 or more players, this restriction gives each player a chance to purchase their share of whatever cube they wish. This rule is motivated by how easily the $1 Pit Team cube is depleted. This rule could potentially also be useful for $2 or even $3 cubes as well.
In 2 player games, I have not imposed a limit because I suspect that if the 1st player buys more than their share of a cube, they will be hurting themselves at least as much as they hurt the other player. I want to leave the game open to such scenarios because I find them interesting.
Choosing driver 04 is not allowed.
(Driver 04’s effect: “Draw up to 3 cubes at once. For each cube drawn, choose one: remove it, place it in your active pile, or put it back into your bag.”)
More races are won with driver 04 than any other driver. What’s more interesting is that the next most-winning driver varies greatly from player to player. Among top players, this could be either driver 01, 02, 03, 07, 09, or 10.
I’m curious which drivers tend to win when driver 04 is not an option.
FWIW, I do NOT think driver 04 necessarily gives its player an unfair advantage. There are scenarios in which driver 04 is definitely not my first choice. Nevertheless, I am interested to see what happens when driver 04 is not allowed.
Violators will be prohibited from participating in my future tournaments.