Q: Multiplayer: How can I vote for a next session or event while driving, without returning to the garage chat?

A1: Start the game and go to the Options ->Multiplayer. You will see a list of various chat phrases. Choose one that you don't think you'll ever use and replace it with the following phrase:
/vote yes

Note: to change the default key binding (CTRL+1-0) go to the Controller options and then click on the word ‘Extra’ at the bottom right of the key binding panel. Scroll down until you get to the Quick Chat # binding that you’ve just replaced with /vote yes. Assign a new shortcut key to it.

A2: Open your player file ([game root]\UserData\YourPlayerName\YourPlayerName.plr) with notepad. Under the section [ CHAT ] edit the following line:

Quick Chat #1="/vote yes"

Pressing CTRL+1 while on track will now result in a ‘yes’ vote. Note that any of the 10 Quick Chat key bindings can be used for this.