KUSA — The University of Colorado A Line opened in 2016 – and for two years, people have been taking the "train to the plane" to Denver International Airport.

The train to the airport costs $9 each way (that price will increase to $10.50 in January 2019) – and takes 37 minutes if you leave from Union Station.

The train is technically the cheapest one way ride to the airport, unless you can convince a friend to drop you off for free.

Though, RTD admits, customers still have to do homework to find the best deal when it comes to transportation to the airport.

“There’s definitely a calculus involved with figuring out what the most cost effective way to get out to the airport,” Nate Currey, a spokesperson for RTD, said.

9NEWS built a trip calculator to help you determine how much various methods cost to get to the airport. This calculator is not precise and is based on very rough estimates. We detail our methodology below.

Can't see the calculator? Click here: http://bit.ly/1ZHq5Bw

METHODOLOGY:

We approximate location using the below addresses:

Downtown Denver: Union Station

South metro area: The RTD Dry Creek Station

West metro area: The RTD Federal Center Station

North metro area: The Wagon Road Park-and-Ride at 11950 Huron St.

Here’s how 9NEWS figured out cost for each method of getting to DIA:

Train: According to RTD’s website, a ride to the airport is $9 – we multiplied that by two (since you'll be traveling both ways), and factored in $2 a day for every day you park at the station. Kids are half off -- so a family of four would be $54 rather than $72, according to RTD (note: RTD clarified this on Tuesday).

Car: We assumed it would cost around $5 in gas to reach the airport (this is a rough approximation) and then assumed you will park in a shuttle lot for $8 a day. For the cost of other lots, go to: http://bit.ly/22zcYoE

SkyRide: We assumed airport fare would cost $9, per SkyRide’s website. Like we did with the light rail, we factored in $2 a day for parking.

Uber: We entered the addresses we used above, and then used this website to estimate the average fare: http://uberestimate.com/

Taxi: We used the taxi fare estimator for Yellow Cab: http://bit.ly/22IRo3D

To calculate time, we used a combination of Google Maps and the tools available on RTD’s website. We did not factor wait time for Uber or taxis, as this can vary. We also assumed you researched when to catch the bus or train first, and weren't late to the station.

For a more accurate look at how to use public transportation to get to the airport, check out the Trip Planner tool on RTD’s website: http://www.rtd-denver.com/GoogleTripPlanner.shtml