Tonight, more than 70,000 people will hop on public buses or private shuttles, find their way through a maze of closed-off streets and finally stand in line to go through the tightest security Invesco Field at Mile High has ever seen.

But Secret Service officials say they are confident that everything will run smoothly for Sen. Barack Obama’s (D-Ill.) acceptance speech, though spokesman Malcolm Wiley conceded that lines might be long.

“Everybody understands the historical significance of this event. It’s not lost on the Secret Service. It’s not lost on the agencies we work with,” he said, later adding: “The thing is, it’s not an uncommon type of event for the Secret Service.”

Wiley compared the event to the Pope’s speech at the Nationals Stadium, Super Bowls and the Olympics — all of which were secured by the Secret Service. The agency “has a great body of experience,” he said, and was able to quickly prepare for Obama’s speech after he moved its venue a month ago from the Pepsi Center to Invesco Field.

About 75,000 people are expected to show up to watch Obama accept the Democratic nomination for president, and hundreds more plan to protest outside. Such crowds often come to Invesco Field, filling the 76,000-seat stadium to watch the Denver Broncos. But at a Broncos’ game, thousands of police officers aren’t scanning credentials or sweeping every crevice for bombs.

As a “National Special Security Event,” the Democratic National Convention has particularly tight security measures. Obama’s high profile adds even more security and the large crowd at Invesco Field means the Secret Service have that many more people to protect.

The stadium will be surrounded by a perimeter much like the one around Pepsi Center, Wiley said. Heavy metal barricades will close off streets, K-9 teams will sweep the area, and snipers will be at the ready.

Delegates will get their own entrance, as will Members, who are being bused to the stadium, Senate Sergeant-at-Arms Terrance Gainer said. Getting around road closures can be tricky, he said, but the Capitol Police have practiced over the past few days.

“The fact that that there’s going to be 75,000 people will be interesting,” he said, but “I think we have a good plan in place.”

Other attendees, however, will be left to find their own way there. They won’t be able to park at the stadium, and most will have to take public buses or private shuttles. They will then have to find their way to one of several entrances, where police will conduct screenings similar to those at the entrances to the Pepsi Center.

At 5:30 p.m., I-25 — the main road to the stadium — will be closed for the entire length of the stadium and beyond, from I-70 to Sixth Avenue. Attendees won’t be able to park, other than in nearby private garages and lots, and they won’t be able to bring in a slew of items ranging from weapons to banners.

The effects of such tight security were seen Tuesday night at the Pepsi Center, when hundreds of reporters, delegates and other attendees showed up for Sen. Hillary Rodham Clinton’s (N.Y.) speech. The mob stretched down Auraria Parkway, overwhelming the media entrance at Auraria and Ninth Street, and forcing police to bus some people to an entrance usually reserved for delegates.

Officials were able to clear the line by about 8 p.m., but the number of attendees was much lower than those expected to show up tonight. Still, the stadium has more entrances and more magnetometers, Wiley said.

Several local police officers agreed that the army of law enforcement officials would be able to handle the crowds. Some also pointed out that so far, protesters haven’t turned up in droves for the convention and have been mostly peaceful — perhaps an indication of tonight’s atmosphere.

The lack of action has been obvious around the Pepsi Center, where groups of officers can often be seen sitting around and waiting. And on Tuesday night, when the mob of attendees descended on the Pepsi Center, plenty of officers were available to corral the crowd into a line.

But that line still took more than an hour to get through.

“Understanding the historical event and the amount of people who will be here, it would be wise and prudent to arrive early,” Wiley said.