Organisers for the inaugural Baltimore Grand Prix have been forced to delay the Friday practice sessions by several hours, as preparations continue to get the temporary 12-turn, 2.4-mile street course into shape for IndyCars to run on.

The original schedule had the first practice session being held from 12.05pm and a second practice session at 4.10pm. These were then pushed back to 3.50pm and 6.05pm respectively, with the first session reduced from 75 to 60 minutes and the second shaved from 60 minutes to 55.

Update: a second timetable revision then combined the two practice periods into a single 90-minute starting at 4pm local time (9pm BST).

Further revisions to the timetable may be necessary if the remaining preparations take longer to carry out than expected.

Cement barriers, fencing and some final barricades were still being erected first thing on Friday morning. Drivers yesterday walked the course and pointed out areas of concern such as high kerbing and tram lines that need attending to before they are suitable for cars to run at speed over them.

Temporary chicanes have now been added to the front straight before the tram lines are reached, and the chicanes have been painted overnight for visibility. Even so, there are concerns that IndyCars will end up getting airborne over the tram lines during the race, as used to happen at the old San Jose and Las Vegas street courses.

"If they'd poured concrete to fill the tracks, we wouldn't need the chicanes," said race director Brian Barnhart, saying that he didn't expect the weekend's programme of events to get underway with USF2000 and Star Mazda support events until midday (5pm BST) at the earliest.

Fortunately there was no actual local damage following Hurricane Irene, which passed over the north-eastern US last weekend and caused widespread damage in parts of the country. However, some of the delays today have been because of work being held up by the passage of the storm through the region.

Arriving too late for the track walk-through but still happy to be back at the race track is HVM's Simona de Silvestro, who has finally sorted out the immigration problem that kept her from competing in last weekend's Indy Grand Prix of Sonoma.

"After a disaster of a week, I'm so happy to be back in the U.S. and reunited with my team," said Simona, who turned 23 on Thursday. "This whole experience was frustrating, but I really want to thank my fans and sponsors for their support."

The exact circumstances of the 'technical problem' that prevented de Silvestro from re-entering the country and being sent back to her native Switzerland have not been officially released, but it's thought that a single immigration official simply refused to believe that Simona was an IndyCar driver and consequently assumed her completed documentation was forged. Simon Pagenaud filled in for de Silvestro at Sonomo and finished 15th place having started in 22nd.

"Unfortunately, she's missed the [Baltimore] track walk so we'll have to get her focused as quickly as possible," said HVM team owner Keith Wiggins. "I'm sure she'll be enthusiastic and hungry."

Tomas Scheckter is also back in the paddock, racing the #07 Redline Xtreme car for SH Racing via a partnership with Dreyer & Reinbold Racing

"Obviously, we can't get on the Baltimore track, but physically it's very good for me," said Scheckter about the difficulties preparing for a brand new, unseen circuit. "That's one thing with street tracks, that no one can test on them. Everybody really has to start fresh."

Mike Conway took a loot at the streets when in Baltimore a couple of weeks ago, and found that one slower section of the course coming out of a hard left-hand turn and leading to pit lane at turn 6 bore his surname.

"I like my chances on that particular stretch, but maybe that's just me," said Conway as he posed with a sign specially made up for his visit temporailiy dubbing this 'Mike Conway St.'

"There are quick corners with long straights leading up to them, which is always difficult but fun," described Conway. "Those are 90-degree corners in third gear, which are going to be quite fast. We go around the baseball stadium and the main straight is four lanes wide that leads into a right-hander, so that will be a passing zone."

Overall, Conway - who won on the streets of Long Beach earlier this year - said that he was looking forward to the maiden Baltimore race. "A new circuit is always fun, and I think it's going to be a lot like the Long Beach atmosphere."