Transportation planners in Denver face an increasingly familiar problem for booming cities in the South and West: Their surging population is straining its roads. Denver has grown nearly 40 percent since 1990, but alternative modes of transportation aren’t yet popular enough to ease traffic.

“We have a finite number of roads and lanes," said Crissy Fanganello, the city’s director of transportation. “That system isn't growing, but the city of Denver certainly is.”

To encourage people to use different modes to navigate the Mile High City, Denver worked with Xerox to create a smartphone app that lets users evaluate all their options and compare the time it takes to use one of those options with another. The Denver Go app is similar to other transit apps, but it gives users even more information -- like the availability of bicycles at bike-share stations, nearby Lyft drivers, close Car2Go vehicles and open parking spaces. In addition to finding the fastest mode, users can also sort results to find the cheapest or greenest options.

“We want to build a transportation and mobility system that is easy, comfortable and convenient,” said Fanganello. “[With this app] people may say, ‘I’m not going to take my car today. I’m going to bike because it’s easier and more convenient.’”

There are already dozens of privately developed smartphone apps -- including Google Maps -- that help travelers navigate city streets in real-time using buses, subways or other transportation modes. But increasingly, local agencies are partnering with private developers in an effort to change both behaviors and perceptions of their cities.

Los Angeles, for instance, also worked with Xerox to develop a similar app there. Portland’s transit agency is working on a project to let riders use its ticketing app to pay for trips with Lyft and Car2Go. New York City hosted a competition last year to encourage developers to build apps for its system.

Even agencies with no formal arrangement with outside app developers can still benefit from good relations with the software companies. Jake Sion of Transit App, which covers 125 cities, said his company often provides local agencies with beta versions of its app before launching in their city. That way, local officials can identify any problems and prepare their own staff for customers using the app.

What's more, private developers are often the first to hear customer feedback on the quality of local service.

“Agencies don’t realize that we are their communication channel to their customers,” said Sion. “They experience the transit systems through our app and apps like us. [Apps are] a great channel to reach their customers.”

That, of course, is one reason local governments are keen to have a hand in developing apps. Denver could eventually use its app to get better data on user behavior or inefficiencies in the transportation network, according to Fanganello. The app eventually might also help improve efficiency by, say, alerting regular drivers that an alternate mode of transportation would be quicker on a day when a car crash causes traffic backups.

But it can be hard for governments to keep up with the speed of technology.

“The city has the vision but not the tech experience,” said Fanganello. “We welcome the help from Xerox, so we can focus on the parts we do well and not do things we have no business being involved in.”

The partnership between Xerox and Denver grew out of the company’s work managing parking for the city. One of the features of the Go Denver app is that it allows users to book parking from their phones.

Xerox developed the app for Denver for free as part of a one-year pilot. Once the year is up, Xerox will have to win a bid to continue providing the service to the city. Xerox hopes to sell its app to other local governments, too.

“Government needs to play this role to coordinate service,” said David Cummins, Xerox’s senior vice president for mobility solutions. “It’s the Nasdaq of mobility. It’s a marketplace where people make their decisions.”