Denver is about 615 miles west of Kansas City on I-70. Eight hours of driving (not counting stops). The toll road runs from I-435 in Kansas City to Topeka. You gain an hour about 400 miles down the road.
The speed limit in Kansas is 70 MPH. In Colorado it is 75 MPH. However, west of Denver, the speed limit changes often (60 MPH or 50 MPH or 40 MPH). Watch it!
You finally can see mountains about 30 miles east of Denver. If a storm front is moving in (west to east), you can see it for miles.
Traffic moves very well on the interstate through Denver, even in afternoon rush hour traffic. Watch the signs.
Once you get west of Denver, the landscape goes from flat to mountainous. What a change! If you and your car are not used to mountain driving, be prepared for your car to feel like it is sputtering as it struggles to accelerate uphill. You will also pass through some tunnels.
The landscape on either side of I-70 is breathtaking. The Colorado River often is just to the side of the interstate. You may find yourself using such words as "magnificent" and "awesome" and "incredible" over and over.
Vail, CO lives up to its reputation as a resort town. It looks like "the rich and famous" spend a lot of time here. It looks like those pictures you've often seen of a small town in Switzerland tucked in a valley of the Swiss Alps.
Rifle, CO is a poor looking town. It sits on what appears to be sandy soil and the mountains (visible in the distance) appear to be nothing but big sand hills.