Andretti Autosport's James Hinchcliffe has been told by that he can recommence light training with his athletic trainer, after his latest evaluation by Verizon IndyCar Series medical consultants on Tuesday.

Medical Director Dr Michael Olinger said that Hinchcliffe is progressing well in his recovery from a concussion that he sustained midway during Saturday's road course race at the Indianapolis Motor Speedway, the result of being struck on the helmet by flying debris believed to be from Justin Wilson's disintegrating front wing.

However, the medical experts have not signed off on the 27-year-old Canadian returning to the cockpit of a race car just yet. He will receive his next evaluation on Thursday to see if he is sufficiently well enough to take part in practice for the Indianapolis 500.

Hinchcliffe has also made his first posts to social networking site Twitter since his accident, thanking fans for all their messages of support.

"Meant a ton to hear from so many. Resting lots & recovering well. Doc says I'm just as dysfunctional as before!" he tweeted.

"Luckily I have a massive nose and it took brunt of the impact! In all seriousness huge thanks to track safety team, IndyCar medical and IU Health staff for the excellent care," he added. "Hope to be back in the buggy soon."

Hinchcliffe is in a race against time to be well enough to take part in this weekend's qualifying sessions for the 98th running of the Greatest Spectacle in Motor Sport. In the past, drivers who have suffered a concussion have been routinely required to stay out of a race car for at least seven days.

Currently the team have former full-time driver EJ Viso substituting for Hinchcliffe in the #27 United Fiber & Data Andretti Autosport. The 29-year-old Venezuelan topped the timesheets in Tuesday's practice sessions, after track time was reduced to just 90 minutes before the onset of heavy rain forced the rest of the day's activities to be cancelled.

"I've taken on the full role," said Viso. "Whatever his crew and engineer had planned to test and experience, I've been doing. It has been a quick adaptation to the team for me and so far it's all been pretty positive.

"My biggest wish is to Hinch and to his recovery," he added. "Hopefully, he's going to be able to make it to the race."

Viso is still optimistic that he might pick up a late entry for the Indy 500 based on his showing so far in practice, even when if and when Hinchcliffe returns to the #27. "If it's a competitive ride, I will of course take it," he confirmed. "There's nothing worse than being lapped every two laps, so for that I truly don't know if it's worth it. It's not like I'm dying to do it, but I'm dying to do well and to have a chance to win."

Hinchcliffe might not be missing much on Wednesday at least, with forecasts once again suggesting rain interruptions to today's scheduled six-hour practice session and possibly even a complete washout.