Ohio cyclist Patricia Kovacs posted an e-mail asking some questions about roundabouts:
Ohio engineers are telling us to use the inner lane for left turns and U turns. Both the FHWA [Federal Highway Administration] and videos available on our local MPO [metropolitan planning organization] website say this. I shared this when we asked for updates to Ohio Street Smarts. If the FHWA and MORPC [Mid-Ohio Regional Planning Commission] are wrong, then we need to fix it.
Would you review the 8 minute video on the MORPC website and let me know what I should do? If it’s wrong, I need to ask them to update it. This video was made in Washington and Ohio reused it.
Looking further into the problem, I see a related practical issue with two-lane roundabouts, that the distance between an entrance and the next exit may be inadequate for a lane change. The larger the roundabout, the longer the distance in which to change lanes, but also the higher the speed which vehicles can maintain and so, the longer distance required. I’m not sure how this all works out as a practical matter. Certainly, turning right from the left-hand lane when through traffic is permitted in the right-hand lane is incorrect under the UVC [Uniform Vehicle Code], and results in an obvious conflict and collision potential, but I can also envision a conflict where a driver entering the roundabout does not expect a driver approaching in the inside lane of the roundabout to be merging into the outside lane.
All in all, the safety record of roundabouts is reported as good (though not as good for bicyclists and pedestrians), but I’m wondering to what extent the issues have been subjected to analysis and research. When I look online, I see a lot of roundabout *promotion* as opposed to roundabout *study*. Perhaps we might take off our UVC hats, put on our NCUTCD [National Committee on Uniform Traffic-Control devices] hats, and propose research?
This post was getting long, so I’ve placed detailed comments on the Ohio video, and embedded the video, in another post. I’m also working on an additional post giving more examples, and I’ll announce it here when it is ready.
Here are some stills from the video showing the conflict between through traffic in the outer lane and exiting traffic in the inner lane.
First, the path for through traffic:
Path for through traffic in a roundabout
Next, the path for left-turning traffic:
Path for left-turning traffic in a roundabout
Now, let’s give that picture a half-turn so the left-turning traffic is entering from the top and exiting from the right:
Path for left-turning traffic in a roundabout, image rotated 180 degrees
And combining the two images, here is what we get:
Conflict between through traffic and exiting left-turn traffic
The image below is from the Manual on Uniform Traffic Control Devices, and shows similar but not identical lane use. The arrows in the entry roadways direct through traffic to use either lane.
FHWA diagram of a roundabout with lane-use arrows.
Drivers are supposed to use their turn signals to indicate that they are to exit from the inner lane — but drivers often forget to use their signals. Safe practice for a driver entering a roundabout, then, is to wait until no traffic is approaching in either lane, even if only entering the outer lane.
A fundamental conceptual issue here is whether the roundabout is to be regarded as a single intersection, or as a series of T intersections wrapped into a circle. To my way of thinking, any circular intersection functions as a series of T intersections, though it functions as a single intersection in relation to the streets which connect to it. Changing lanes inside an intersection is generally prohibited under the traffic law, and so, if a roundabout is regarded as a single intersection, we get the conflicts I’ve described.
Sometimes, dashed lines are used to indicate paths in an intersection, when vehicles coming from a different direction may cross the dashed lines after yielding right of way or on a different signal phase. More commonly, a dashed line indicates that a driver may change lanes starting from either side. The dashed lines in a two-lane roundabout look as though they serve the second of these purposes, though they in fact serve the first. These are shorter dashed lines than generally are used to indicate that lane changes are legal, but most drivers don’t understand the difference.
That leads to confusion. If you think of the roundabout as a single intersection, changing from the inside to the outside lane is illegal anywhere. If you think of the roundabout as a series of T intersections, changing lanes should occur between the entries and exits, not opposite them –though there is also the problem which Patricia mentioned, that a small two-lane roundabout may not have much length between an entry roadway and the next exit roadway to allow for a lane change. That is, however, much less of a problem for bicyclists than for operators of wider and longer vehicles. It would be hard to construct a two-lane roundabout small enough to prevent bicyclists from changing lanes.
My practice when cycling in conventional two-lane traffic circles — and there are many in the Boston, Massachusetts area where I live — is to
- enter from the lane which best leads to my position on the circular roadway — either the right or left lane of a two-lane entry;
- stay in the outer lane if leaving at the first exit;
- control the inner lane if continuing past the first exit;
- change back to the left tire track in the outer lane to prepare to exit.
That way, I avoid conflict with entering and exiting traffic in the outer lane, and I am making my lane change to the right in the slow traffic of the circular roadway rather than on the straightaway following it. This is what I have found to make my interactions with motorists work most smoothly. Why should a bicyclist’s conduct in a roundabout be different?
It is usual to be able to turn right into the rightmost lane of a multi-lane rodway while raffic is approaching in the next lane. I don’t know of any other examples in road design or traffic law in the USA where a motor vehicle is supposed to turn right across the lane where another motor vehicle is entering it. Bike lanes are sometimes brought up to intersections, though the laws of every state except Oregon require motorists to merge into the bike lane before turning. The illustration below, from Dan Gutierrez, depicts the problem.
Right hook conflicts, from Dan Gutierrez’s Understanding Bicycle Transportation video and course.
Applicable sections or the Uniform Vehicle Code are:
- 11:304 (b) — passing on the right is permitted only when the movement can be made in safety.
- 11:308 (c) — a vehicle shall be driven only to the right of a rotary traffic island.
- 11:309 (a) — no changing lanes unless it can be done in safety
- 11:309 (d) — official traffic control devices may prohibit lane changes
- 11:601 (a) Right turns – Both the approach for a right turn and a right turn shall be made as close as practicable to the right-hand curb or edge of the roadway.