Whenever you travel to Denver you encounter the I-70 express lane and here are three things you may not know about this extra lane.

It's been nearly three years since the Colorado Department of Transportation opened the express lane toll road on I-70 west of Denver. I have yet to drive in that lane even once, but there are people that use it.

Part of the reason I avoid the express lane on I-70 is that I don't want to pay "extra' to perhaps save myself a handful of minutes of travel time. Whatever the toll may end up being is likely not worth the chance to make up a small amount of time. I'm rarely in that big of a hurry.

The other reason I avoid the express lane is that I don't fully understand how it works. Most of the time when I go to Denver, the express lane is "closed". Does that mean the lane is not being tolled at that particular time, or does that mean you should not be in that lane at all? And, while we are wondering aloud, what is it that determines whether the express toll lane is open? Why isn't open all the time?

For the answers to these questions, I went straight to the Colorado Department of Transportation, and here is what Communications Manager Megan Castle told me.

The first thing you need to understand that you must pay a toll if you use the I-70 Express Lane, even if you have three or more people in the car. Generally, with express lanes in Denver, carpoolers and motorcycles can use them for free. That is not the case on I-70.

Secondly, the  I-70 Express Lane is only open during peak travel times - like holidays and weekends - which comes out to around 100 days a year.  When it is "closed", it becomes a shoulder and is not to be used. The "closed" express lane does not simply mean it's not being tolled at that time. There are signs along the way which clearly state if the express lane is open or closed.

So, why isn't the I-70 Express Lane open all the time? Well, that's kind of a long story, but essentially it comes down to the original intention of the express lane - to help alleviate congestion during peak travel times. The express lane was constructed using part of the shoulder of the interstate, which limits safe stoppage areas for disabled vehicles as well as emergency vehicles. When the express lane is closed, it reverts to being a shoulder that can be utilized for emergencies.

If you have an Express Toll account,  you will typically pay anywhere from $3 to $15, depending on the volume of traffic. Even if you don't have an account,  you can use the express lane, but you will pay the regular toll, plus administrative costs that come from looking up the license plate and billing the motorist. You'll end up paying about twice as much.

They say express lane users can save about 30 minutes of time, but that estimate largely depends on the volume of traffic and if the interstate is experiencing some high traffic delays.

So, now you know what you need to know about the I-70 Express Lane, and maybe you will feel more comfortable about using it - or not using it.