Organizers of President Barack Obama’s second inauguration say they’ve made changes in security and logistics that should prevent some of the problems seen in 2008, but the size of the crowd, expected to be vastly smaller than four years ago, could be the biggest factor that determines how smoothly things run.

The president’s first inauguration saw an estimated 1.8 million people descend on the city, but this year’s projections are much lower — 800,000 at the top end. While that’s a relief to some organizers and security overseers, it’s not good news for everyone.

“We get tax revenue from people who come to the District, so we want those 1.8 million people,” said Charles Allen, a spokesman for D.C. Councilmember Tommy Wells. He acknowledged, however, that the smaller number of visitors will be less of a challenge for planners. “People get the sense that it’ll be easier to manage than the crush of people four years ago.”

Security officials said they’re approaching this inauguration as seriously as the last one, adding that they have no information pointing to credible threats to the event.

Some procedures, however, have changed thanks to the lower projected turnout. While 2009 saw most of the bridges that connect the city to Virginia closed, only the Memorial Bridge will be limited to foot traffic this year. Some, including the South Capitol Street Bridge and the Chain Bridge, will remain open, while others, such as the 14th Street Bridge, will be diverted or restricted.

The areas around the Capitol, White House and National Mall will still be subject to widespread road closures and have set pedestrian walking routes running through them. At the Capitol, organizers are reaching the final stages of preparation, Senate Sergeant-at-Arms Terrance Gainer said.

“I won’t say we’re completely ready yet, but we’re close,” he said Wednesday. “If I had to put a number on it, I’d say we’re 95 percent there. People are going through and checking things like lighting, the carpet, security issues. It’s like a wedding. You’re working just about up to church time.”

What all of the event’s organizers are looking to avoid this year is another “Purple Tunnel of Doom,” where 1,000 ticketed attendees were stuck in the Third Street Tunnel and missed the 2009 inauguration ceremony.

The tunnel itself won’t be a problem — police decided to close it for the event — and the smaller crowds means less likelihood of a repeat. Gainer said he thinks the incident achieved an unfair level of notoriety, considering the number of people stuck versus the total attendance. But he said that, this time around, organizers brought in experts on monitoring and moving large crowds to inform their decisions.

“I won’t deny how tough it was for people who got stuck in the tunnel. I’ve talked to some of them,” Gainer said, adding that organizers were “very much aware of how to avoid that specific problem.”

The result of their advice, he said, is an increase in signs and workers telling people where to go, with the goal of getting them from their Metro station or other point of entry to their destinations as quickly as possible. Gainer said “wayfinder” workers will screen crowds as they approach the Capitol, trying to make sure that everyone is heading toward the correct gate and trying to avoid having people arrive at the wrong place, then having to fight through a crowd to leave.

“An action somewhere has a ripple somewhere else,” he said. “Anytime someone decides to open a gate, close a gate, delay a gate, that ripples all the way back through the streets and into the Metro system. So knowing about all of that as it happens allows you to call an audible when you need to.”

Organizers have also focused on getting advance information to attendees about how to get where they need to go. “That really wasn’t the focus four years ago,” Gainer said.

Brian Leary, spokesman for the Secret Service, the lead security agency for the event, said organizers are hoping that inauguration apps for smartphones and social media could play a helpful role in moving people this year. Agencies are using a common hashtag, #inaug2013, for communications, he said.

“Obviously social media is more prevalent now than in 2009,” Leary said. “It’s a great way to get information out to the public. There is a balance between moving people quickly and efficiently but also safely, so the best option is to communicate with them.”

Still, some delays will be inevitable, especially for ticketed attendees approaching the nearly 200 metal detectors the Secret Service is setting up around the Capitol.

“I think what people need to keep in mind is to give a lot of time to get where they need to go and be patient,” said Shennell S. Antrobus, a spokesman for the Capitol Police. “Dress appropriately for the weather and enjoy the day.”

Antrobus said attendees are likely to have a smoother experience if they check the list of items generally prohibited from the parade route and the more restrictive list for the Capitol. Umbrellas, for example, are permitted along the parade route but not at the Capitol.

He said attendees can make the experience more pleasant for one another if they pay attention to signs, avoid items that would slow down security checkpoints and stay away from areas they won’t be allowed into. “If you do not have a ticket,” he said, “do not go to Capitol Hill.”

Emily Holden contributed to this report.

Corrects the rank of Shennell S. Antrobus.