Will Power got IndyCar's first visit to the streets of Baltimore under way by topping Friday's delayed opening practice session.
The Penske driver spent much of the 90 minutes trading turns at the top of the timing screens with title rival Dario Franchitti before finally settling matters in the final moments with a 1:23.613, putting him just 0.0783sec clear of the Scot's time.
"You are working the entire time and it is a pretty cool track," said Power, who won the Indy Grand Prix of Sonoma last weekend to tighten his championship points duel with Franchitti. "They did a really good job creating the circuit. It takes a lot of commitment and there are several technical bits. It's bumpy and I think it will be a great race.
"It is very tricky in certain places, but that is typical of a street course. It is challenging with a lot of corners and the technical requirements."
A late push from Helio Castroneves was rewarded with third ahead of Ryan Hunter-Reay, who had enjoyed a brief stint on top before being demoted by Penske and Ganassi.
"I like the layout of the circuit. It's very cool and very challenging," Castroneves said. "Some of the surface is so smooth and other parts are pretty rough, but every street course has its challenges, especially the first year. We certainly have a few things to work on with the No. 3 car, but we're going in a good direction."
Hunter-Reay's Andretti Autosport teammate Mike Conway was fifth quickest, with Graham Rahal sixth ahead of Takuma Sato. James Hinchcliffe, Tony Kanaan and Sebastien Bourdais rounded out the top 10.
The track claimed a couple of high-profile scalps early on, starting with Ganassi's Scott Dixon. The New Zealander took the unfortunate honor of being the first driver to crash at the circuit when he clouted the outside barrier at Turn 4, ending his afternoon after just three laps.
Ryan Briscoe's participation was cut short soon afterward, the Penske racer clipping the tires on the way into the Turn 6 chicane. Both incidents triggered full-course yellows, as did a spin from Tomas Scheckter at Turn 8 and, later, simultaneous spins at Turns 1 and 6 by EJ Viso and Giorgio Pantano, although all were eventually able to get going again.
An additional hour of practice will precede Saturday's qualifying sessions.
Pos Driver Team Time Gap
1. Will Power Penske 1m22.138s
2. Dario Franchitti Ganassi 1m22.216s + 0.078s
3. Helio Castroneves Penske 1m22.285s + 0.147s
4. Ryan Hunter-Reay Andretti 1m22.603s + 0.465s
5. Mike Conway Andretti 1m22.726s + 0.588s
6. Graham Rahal Ganassi 1m22.739s + 0.601s
7. Takuma Sato KV 1m22.971s + 0.833s
8. James Hinchcliffe Newman/Haas 1m23.008s + 0.870s
9. Tony Kanaan KV 1m23.199s + 1.061s
10. Sebastien Bourdais Dale Coyne 1m23.303s + 1.165s
11. Simona de Silvestro HVM 1m23.373s + 1.235s
12. Alex Tagliani Sam Schmidt 1m23.408s + 1.270s
13. Charlie Kimball Ganassi 1m23.696s + 1.558s
14. Giorgio Pantano Dreyer & Reinbold 1m23.732s + 1.594s
15. Tomas Scheckter Sam Schmidt Dragon 1m23.767s + 1.629s
16. Marco Andretti Andretti 1m23.781s + 1.644s
17. Sebastian Saavedra Conquest 1m23.812s + 1.674s
18. Ryan Briscoe Penske 1m24.203s + 2.065s
19. Oriol Servia Newman/Haas 1m24.209s + 2.071s
20. JR Hildebrand Panther 1m24.246s + 2.109s
21. Vitor Meira Foyt 1m24.268s + 2.130s
22. James Jakes Dayle Coyne 1m24.408s + 2.270s
23. Ernesto Viso KV 1m24.414s + 2.276s
24. Danica Patrick Andretti 1m24.500s + 2.362s
25. Martin Plowman AFS/Sam Shmidt 1m25.051s + 2.913s
26. Scott Dixon Ganassi 1m25.070s + 2.932s
27. Ana Beatriz Dreyer & Reinbold 1m25.894s + 3.756s
28. Ed Carpenter Sarah Fisher 1m26.026s + 3.888s