A shared left turn lane is a center lane on a road that drivers traveling in either direction can use to make left turns. You’ll most often see it on busy three-lane or five-lane roads, sitting right in the middle between opposing traffic flows. Its formal name in traffic engineering is a two-way left-turn lane, or TWLTL, and its primary job is to give left-turning drivers a place to wait for a gap in traffic without blocking the cars behind them.
How It Works
On a road without a center turn lane, a driver waiting to turn left into a driveway or side street has to stop in the travel lane. Every car behind them has to stop too, which creates rear-end crash risk and backs up traffic. A shared left turn lane solves this by giving that driver a dedicated space to pull into, slow down, and wait for an opening in oncoming traffic. Because both directions share the same lane, a driver heading north and a driver heading south could both be using the lane at the same time, just at different points along the road.
The Federal Highway Administration has studied these lanes specifically for their safety benefits. They reduce rear-end crashes caused by vehicles slowing or stopping to turn left, and they also reduce head-on collisions by creating a buffer zone between opposing directions of travel. States like Arkansas and California have installed them on two-lane roads for exactly these reasons.
How to Identify One
Shared left turn lanes have a distinctive marking pattern that looks different from any other lane on the road. Each edge of the lane is marked with two yellow lines side by side: one solid and one broken. The broken line always faces inward (toward the center of the turn lane), and the solid line always faces outward (toward the adjacent travel lane). This creates a pattern where, from above, you see solid-broken on one side and broken-solid on the other.
Inside the lane, white arrows point in both directions, usually painted in pairs with one arrow facing each way. These arrows appear at the start of the lane and at intervals along it. Road signs reading “Center Turn Lane” or showing a left-turn arrow are also typically posted alongside the pavement markings.
If you see this combination of inward-facing broken yellow lines, opposing white arrows, and signage, you’re looking at a shared left turn lane.
Rules for Using It Correctly
The lane exists for one purpose: preparing for and completing a left turn. You enter the lane when you’re getting ready to turn left into a driveway, parking lot, or side street, and you leave the lane by completing that turn. In most states, you can also use it to prepare for a U-turn where U-turns are otherwise legal.
There are several things you cannot do in this lane:
- Pass other vehicles. The California DMV states plainly that the center left turn lane “is not a regular traffic lane or passing lane.” Using it to get around slower traffic is illegal everywhere.
- Travel in it. You shouldn’t drive along the lane as if it were a through lane. Missouri law, for example, caps travel in the lane at 500 feet. The general rule across states is that you enter the lane only when your turn is close, not a quarter mile before it.
- Use it as a merge lane. When turning left from a side street onto a road with a center turn lane, you cannot pull into the center lane and sit there waiting for a gap in traffic to merge into the travel lane. You need to wait at the side street until you can complete the full turn into a travel lane.
Entering From a Side Street or Driveway
This is the scenario that confuses the most drivers. You’re sitting at a driveway or side street, wanting to turn left onto a road that has a shared center turn lane. It might seem logical to pull into the center lane first, then merge into traffic once a gap opens up. But in most states, this is not how the lane is intended to be used. The center lane is designed for vehicles already on the road who need to turn off of it, not for vehicles entering the road who want a staging area.
The practical issue is safety. If you’re sitting in the center lane waiting to merge, a driver already on the road may pull into that same spot to make their own left turn. Neither of you expects the other to be there, and the closing speeds can be high. The correct approach is to wait at the side street until traffic is clear enough to complete your turn directly into a travel lane.
Common Mistakes to Avoid
The biggest mistake drivers make is treating the center turn lane like a travel lane. Entering it early and cruising along while looking for your turn creates a head-on risk with someone doing the same thing from the opposite direction. Get in, slow down, turn. That’s the sequence.
Another common error is entering the lane too late, cutting across at a sharp angle at the last moment. Signal early, check for oncoming vehicles already using the lane ahead of you, and merge into the lane smoothly before slowing for your turn. You share this space with drivers coming from the other direction, so scanning ahead in both directions matters more here than in a standard lane.
Finally, remember that the lane’s shared nature means someone could be occupying your intended space at any time. Before you move into it, check not just the traffic beside you but also any oncoming vehicles that may already be waiting in the lane further ahead. A brief shoulder check can prevent the kind of nose-to-nose standoff that makes these lanes stressful for newer drivers.