Kaido 2 info From genki's site:

"Highway battle 2 CR ' with, the real time battle in two human simultaneous plays due to picture top and bottom ニ division is possible. Of course, gathering the saving data, the battle it is possible with the respective machine which the prayer enhances to do."

CONQUEST (コンクエスト) mode
The noon make the prize with official race/lace, the night to shave the rival of entire country and the ridges on the side of a sword, aim toward "the man of highway most speed"!
* RECORD CHALLENGE (record challenge) mode
Speed and beauty of the drift are competed to ultimate. Net ranking opening schedule!
* VS BATTLE (VS battle) mode
Uses split screen system with the VS mode which, the real time battle of the friend possibility!
* REPLAY THERTER (リプレイシアター) mode
Until the gorgeous running heart it goes, it is skillful. You cannot miss even in research of running!
* SOUND CREATE (sound create) mode
Loading the BGM compilation tool of the new axis. Attack the pass with original BGM!

"With VS battle mode, three battle systems selective possibility. Goal aiming, it does race/lace, "SPEED KING MODE" and CA (the cornering artist) the point is competed, "CA KING MODE" and SP (the spirit point) victory or defeat is decided with the battle, "SP KING MODE" is prepared."

So split screen is definite, Also I got a little info from the Q&A section.

Q."When you have used, horsepower of the car fell."
A. "When "ヤレ" (degree of fatigue) accumulates with usage condition it has reached the point where horsepower falls."

So basically, shit wears out when you race. I think that's pretty cool.

Here's some clips: http://www.genki.co.jp/games/kb2/movie/index.html