Julia from Littleton writes, “What's driving you crazy? My sister and I have a disagreement I am hoping you can settle. Near Green Mountain, C4-70 is a three-lane highway until you hit the dotted white line indicating you are now in the exit only lane for Morrison Road. I say you can keep going and eventually merge left to continue on 470. My sister disagrees and thinks that the ones who ride the right-hand lane and then merge over right before the Morrison exit are being jerks. Can you answer this so I can show my sister the answer, whatever it is? I love Jayson Luber and am betting he can answer this!”
Julia, before getting into the merge debate, let's first discuss the way the highway is designed to work. While traveling eastbound on C-470 from I-70 — or 6th Avenue — towards Morrison Road, there are three all-purpose travel lanes. At about the point where the grandstands at Bandimere Speedway are visible, the long dashed lines separating the farthest right lane from the center lane change to short dashed lines. That indicates the far right lane has become an exit only lane that will end at Morrison Road.
When a driver sees the dotted lines, that person must choose to either merge one lane to the left, if their intent is to continue east on C-470, or stay in that lane, if their intent is to exit at Morrison Road. Where that decision happens is left to driver discretion and traffic volume. The dotted lines run for about 2,000 feet, which is nearly half a mile, allowing for plenty of time for drivers to merge left if they want to continue on C-470.
That's how the roadway is designed under normal traffic volume, but it's not what happens in practice, especially in heavy traffic every afternoon. The issue your sister brings up is that drivers like her, knowing they want to continue east on C-470, get over early — well before the dotted lines start and hate to see “jerk” drivers use that exit only lane to bypass and then cut in front of all the drivers waiting in the slow traffic.
The concern from the Colorado Department of Transportation with this situation is when drivers cut over from that right exit lane at the last minute into the center lane, they become the major contributors to the 15- to 20-minute travel time between Alameda Parkway to Morrison Road that happens during every evening commute. Meanwhile, the Colorado State Patrol is concerned that when the drivers cut into traffic at the last minute, they contribute to the high number of rear end crashes in the area.
This type of merge on C-470 will only work as designed if the drivers who know the right lane will eventually become an exit lane get over before or shortly after the right lane becomes an exit only lane in moderate to light traffic. Drivers need to get over much earlier in heavier traffic. That movement also relies on drivers in the middle lane allowing the right lane drivers to merge over in their lane. That all too often does not happen in moderate traffic and rarely ever happens in heavy traffic. Drivers would need to behave with more civility on the roadways for that to be a common occurrence.
Remember, it can’t be assumed that all drivers on eastbound C-470 know that the right lane ends at Morrison Road before they see the dashed lined turn into dots. They will need to make the honest merge to the left when they see the change in the lane lines to exit-only dashes if they want to continue on eastbound C-470.
This is where a zipper merge comes into play. That’s where drivers take turns at a merge point into one lane like behind a crash or at a construction zone. The zipper works where drivers use both lanes all the way to the blocked lane and then merge at that point. They are not supposed to merge early.
This C-470 merge functions differently than the classic zipper. The merge on C-470 for drivers continuing eastbound in light to moderate traffic flow should happen before or shortly after the transition to the exit only lane. However, in heavy traffic, drivers routinely go much farther towards Morrison Road and cut over to the left in front of a hundred other drivers when they see the smallest sliver of space.
Could anyone consider those drivers inconsiderate? Definitely. Again, drivers can’t assume every driver knows that lane is going to end, but it's probably safe to think most do and are just trying to save time at the expense of all the other drivers slowly crawling along in the two remaining lanes on eastbound C-470.
There are possible solutions to the problem. More advanced warning signs is one way to give drivers an early heads up about the eventual end of that lane at Morrison Road. Getting drivers to pay attention to those signs is another story.
CDOT could extend that third lane as a bridge across Morrison Road then over to Colorado Highway 285, but that would cost lots of money and only extend the merge problem with three lanes into two over to Colorado Highway 285. Reading through complaints to CDOT from drivers who regularly use that section of C-470, they would all like to see the continuation of the third lane across Morrison Road to Colorado Highway 285.
Colorado State Patrol could also increase enforcement in that lane, but merging at the last minute isn’t illegal unless a driver does it over the solid white line at the gore point.
CDOT had a plan to improve that entire area, but funding for any widening or improvements between Colorado Highway 285 and Morrison Road have been pushed back to beyond 2027. There were also plans to rebuild all of C-470 between Wadsworth Boulevard and I-70, but that project is also many years and many more millions of dollars down the road.
Both of you have a point in this argument, so maybe consider this one a draw where you both are right.
Denver7 traffic anchor Jayson Luber says he has been covering Denver-metro traffic since Ben-Hur was driving a chariot. (We believe the actual number is over 25 years.) He's obsessed with letting viewers know what's happening on their drive and the best way to avoid the problems that spring up. Follow him on Facebook, Twitter or Instagram or listen to his Driving You Crazy podcast on iTunes , Stitcher , Google Play or Podbean.