RAGE design director Matt Hooper has said when developing the game, the team at id Software originally focused on creating the single-player mode, and as time progressed, they found it would be even more fun if co-op were added.
Speaking with Gamespot at TGS, Hooper said there will be plenty to do in the single-player campaign especially when you venture off the beaten path of the main storyline. Basically, he implied that the single-player campaign wasn't shortened in order to focus on multiplayer.
"Our goal is to create a lengthy campaign, probably about 15 hours," he said. "But for a shooter, that time count is significant because most shooters are eight hours or less. If you do the game's side quests, that adds up to 20 to 25 hours. We put a lot of focus for this significant amount of game alongside the co-op and vehicles.
"Online components like Combat Rally and Legends of the Wasteland would be a good match for the Rage world. We still care a lot about deathmatch and on-foot combat as a studio, but that kind of sticks to Doom, Quake, and those franchises.
"We're really happy with how multiplayer turned out, but it was more on concentrating on single-player and thinking: 'That works pretty well. Wouldn't that be fun to do that with a buddy?' We added split-screen mode and online co-op campaigns as a result.
"The vehicles were there because there weren't any parallels to draw from. We tried the vehicles, physics and all, and we liked it. Those are just bonuses for the players."
Hooper goes on to say RAGE has ample diversity, as there's "always something new," around the bend.
"We have the visuals that then matches the gameplay, and we have a big toolbox consisting of the gadgets, the weapons, and the ammo types," he said. "We're not aiming for a typical one-look one-feel shooter."
RAGE is out the first part of October on PC, PS3, and Xbox 360.