If you rely on public transit to get around, chances are you've heard of Citymapper.

It's by far the best app for navigating the chaos that can be the subway and city bus system. I use the free app in New York City — it's available in more than two dozen other cities, too — and it's saved me countless times from having no idea how to get where I'm going.

On Monday, Citymapper got a huge update that's going to save me and many other commuters a lot of time. The app will now tell you exactly where to get on the subway train so you'll be in the ideal spot, by the exit closest to your destination, when you get off.

For example, if your're going to a friend's apartment, the app may tell you to get on the rear of the train because that station exit is closest to your friend's apartment.

In case you've never used Citymapper, here's how it works: you tell the app what city you're in, and then it taps into all of the available forms of public transit (subways, express trains, buses, ferries) to help you get places. It also gives you estimates for taxis and Uber cars in your area, should you opt not to use public transit.

Citymapper is currently available in New York, the San Francisco Bay Area, Los Angeles, Chicago, Boston, Washington DC, Philadelphia, Singapore, Hong Kong, and 18 other cities around the world.

Now you can see the optimal place to enter and exit a subway station along with where to enter the train carriage — that's a game changer.

Not every route will have the new train boarding feature, but you can help Citymapper support more routes by providing feedback in the app.

Apple's update to the Maps app in iOS 9, the forthcoming operating mobile system, tells you the best place to enter and exit the subway in a few cities, but no other transit app tells you the best place to be on the train itself.

An update to Apple's Maps app coming later this year will show you in some cities the best place to exit and enter the subway. Screenshot

Citymapper's newest update also lets you bookmark more places besides your work and home addresses, which is helpful for quickly getting to places you frequent.

You can also set a manual alarm for getting off the train at the right time when you don't have cell service.

No more missing your stop because you fell asleep.

There's also a new map view in the "Near" section of the app that is basically like a God view of your entire city's public transit options.

It will give you a great view of train and subway stations as well as bus stops.

You're about to become a commuting boss.