Now in its third beta, a comprehensive San Francisco transit map heralded by The Atlantic's CityLab has the power to take a starting point in the city and estimate how far you can get in a given window of time and a given set of conditions. Those conditions include best, average, and worst transit cases, times of day, and even transit as it is now versus how it will be with anticipated improvements in coming years.

The "Interactive Transit Service Map of San Francisco" comes from former Berkeley grad student Dan Howard and former Muni transportation planner Chris Pangilinan, now of the New York City Transit Authority. "We're not selling 10 seconds of travel time," Pangilinan told CityLab of his jobs in transportation planning, "What we're actually providing to the public is access to the city." This map, then, is an illustration of that access. Here's how to navigate it.

To start, click on any intersection in the city. You probably want to leave the "baseline" service on the right as is, for now. The four dots on the left are the zoom feature, so experiment with those first.

Once you've clicked your starting point, adjust the bottom slider to an allotted amount of time to see how far you'll be able to get in that window. Here's 20 minutes from around 16th and Folsom.

Now, expand to a new time to see how much farther you can get with a bit more time. Here's 33 minutes from the same spot. Beautifully illustrated, the colors of your reach correspond to the time it would take you to get there.

Next, experiment with best and worst cases. Yes, those the angel bus and the devil bus icons. One of the big takeaways is right here. On a good day, you can take SF public transit much, much farther. In fact, it's almost a different system. You might even need to zoom out with those four red dots for best case service.

Now for the worst case, another whole different system... but one with which you may be well acquainted.

Yep, on a day like that, you might want to walk. To see what that would look like in the same time period, click the walking guy icon.

Remember, transit is a whole different animal at night. You can play around with the time of day, check out reliability, and even see how many jobs you can access from a particular point given all the other conditions. Safe travels!

Interactive Transit Service Map of San Francisco