Practice and qualifying sessions for this weekend's Shell and Pennzoil Grand Prix of Houston have had to be rearranged after time was lost on Friday assessing an issue with turn 1 on the 1.683-mile, 10-turn temporary street course in Reliant Park.

The surface in turn 1 proved to be too bumpy to safely run IndyCars at speed without the danger that they could become airborne and be sent out of control into the wall. The issue was first detected by drivers in the Pirelli World Challenge support event which made the first run on the track on Friday morning.

The affected area hadn't been accessible to the organisers to assess until the park was cleared during the week, with work not being completed until late on Thursday evening, explained Martyn Thake, director of operations for the event promoter.

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"A facility like this used as much as it is, it was an area we weren't able to explore too closely until we took over the facility," said Trask. "There have been so many things moving and interlocking at the same time.

"It was a unique challenge the last 96 hours turning the parking lot into a racetrack starting right after the [Houston] Texas game," he added, referring to the NFL game held at Reliant Stadium at the weekend.

As a result, the first Firestone Indy Lights practice session was cancelled while the surface was investigated, and the start of the first IZOD IndyCar Series practice session delayed by two and a half hours until the race organisers decided upon a course of action.

"A temporary [tyre] chicane has been placed on front straight to allow for practice," reported Brian Barnhart, IndyCar's president of race operations. "A more permanent fix will take place this evening." That will involve carrying out overnight grinding of the affected area to remove the problem.

"I think the solutions we've come up with will work out fine," insisted Trask.

However the Friday morning delay does cause knock-on effects both to the timing and the content of the doubleheader weekend, as the timetable is packed with other events and has little slack to absorb the initial hold-up.

The original single 90-minute IndyCar practice will now take place in two 45-minute sessions on Friday at 1pm local time (7pm BST) and 4.30pm (10.30pm BST) with USF2000, PRO MAZDA and Indy Lights practice being held in between.

The lack of time means there is no slot for the planned qualifying session for the first of the two IndyCar races of the doubleheader. Instead, qualifying will take place on Saturday morning at 10.45am (4.45pm BST), but there is insufficient time to stage a full three round elimination/Firestone Fast Six qualifying process and so instead the cars will be split into two groups and each have half the session to set timed laps, with the fastest driver of the session winning pole. The race will take place as scheduled at 2.30pm (8.30pm BST).

Qualifying for race 2 will now replace the Sunday morning warm-up session and is scheduled for 8.45am (2.45pm BST) and will take a similar 30 minute format as the first. The second race will get the green flag shortly after 12.30pm (6.30pm BST) on Sunday afternoon.

Both races will consist of 90 laps each, and race 1 will feature a standing start.