Australia's Will Power managed to avoid a horror last-lap crash at the Houston Grand Prix to clinch his second IndyCar victory of the season on Sunday.

Power held off New Zealand driver and now series leader Scott Dixon for a majority of race two of the Houston double-header, having jumped ahead of the Kiwi on an early restart.

But the Penske pilot's efforts were overshadowed by an accident involving four-time IndyCar series champion Dario Franchitti on the final lap.

Franchitti's car went airborne and slammed into the safety fencing before coming to a halt in the middle of the street circuit track.

The Scotsman was stretchered off the track and taken by ambulance to the nearby Houston hospital.

Race officials said Franchitti was "awake and alert" but did not go into details on his injuries.

His team owner Chip Ganassi said Franchitti injured his ankle and back.

Power, who sits one spot ahead of Franchitti in seventh on the championship standings, said the incident reminded him of an accident in 2011 at Las Vegas which killed Dan Wheldon.

"I just saw Dario's car and him sitting in it with a lot of damage, and yes, that's what it reminded me of," said Power, who broke his back in the Las Vegas accident.

"I hate seeing that. We try to keep these cars on the ground.

"I just hope he's OK. But it was a very good day (on the track)."

Despite losing out to Power, Dixon's second-place finish was enough to shoot him ahead of Power's teammate Helio Castroneves on the season's standings by 25 points.

Brazilian Castroneves had a disastrous afternoon, slipping down from pole position to 23rd after suffering gearbox issues for the second day in a row.

He had held the lead going into the weekend's two races.

Dixon will now be chasing his third IndyCar title at the last race of the season in Fontana, California, on October 20.

"All in all it's been a pretty decent weekend," Dixon said.

"It's been a good turnaround in points for us, but it's still going to be a tough weekend in Fontana - 25 points can go anybody's way."