CLICK: Full practice 1 results
Will Power set the pace in the first of two 45 minute practice sessions on Friday ahead of this weekend's Shell and Pennzoil Grand Prix of Houston.
The Penske driver set a time of 1:00.4427s (97.322mph) on the 1.634-mile, 10-turn temporary street circuit, putting him 0.2529s clear of Schmidt Peterson Hamilton Motorsport's Simon Pagenaud who claimed runner-up honours ahead of KVSH Racing's Sebastien Bourdais.
"You have to be very aggressive on the street courses because that's where the speed is," said Power. "You have to have good strategy. Aside from a part failure, having the wrong strategy can keep you from winning more than anything."
Power won the second race in last year's Houston doubleheader, which took place later in the year in October. Moving the race to mid-summer this year has given rise to concerns about the effect of the blistering Texas heat, although Friday was relatively cool and there is even a threat of rain for later on Friday. However the forecast for the rest of the weekend is dry - and hot.
In total, 16 of the 23 cars at work this weekend were within one second of Power's flying lap in first practice, including former GP2 driver Luca Filippi who is making his debit for Rahal Letterman Lanigan Racing this weekend.
There were five different teams in the top five, with AJ Foyt Racing's Takuma Sato in fourth place and Target Chip Ganassi Racing's Tony Kanaan in fifth. In the manufacturer stakes, Chevrolet were just ahead with six cars in the top ten to Honda's four.
The session saw a brief red flag while an issue with a track seam was attended to. The organisers will also look at grinding down one of the kerbs on the course overnight after Power was sent airborne midway through the session.
In addition, there was a minor racing incident when Graham Rahal was caught out by a slow-running Scott Dixon, and the RLL #15 ended up making light contact with the rear of the Ganassi #9 car.
A second 45-minute practice is scheduled for 2pm local time (8pm BST), and it will be followed by a ten-minute standing-start practice for Saturday's race 1.
Qualifying for race 1 will take place at 10am (4pm BST) on Saturday morning with the race itself getting underway at 2.45pm (8.45pm BST). In the UK, the race will be shown live on ESPN.
Full practice 1 results