Saturday, July 24, 2010

Monona Drive: The Walls and Sight Distance

Some questions have been raised about the intersection features on Monona Drive and whether drivers on the side roads have adequate sight distance. It's a natural question and I know it looks like the walls will obstruct the view, but the answer from the engineers is a definite 'yes'.

The side roads intersecting Monona Drive within the project limits were re-checked for Intersection Sight Distance (ISD) based on the plans and the criteria in the Facilities Development Manual Section 11-10-5 . These intersections were evaluated for the conditions in Stage 4, Stage 5, and the final (completed) condition per the plans. ISD for the posted speed of 30 mph is met or exceed during construction while an ISD of the design speed of 35 mph is met or exceeded in the final condition. No intersections were found to have substandard ISD.

The Facilities Development Manual is WisDOT's manual of roadway standards. You can view it at Free registration is required to access the DOT extranet.


  1. I think they are a tad bit obstructive despite what the experts say. I had to pull way forward into the cross walk in order to see to the right (at Panther Trail). If there was a "do over", I would move it back. I would not spend money to change it now but I do have to agree that they do obstruct your vision of the road

  2. I had the same reaction at Owen Road, but we are both being mislead by the fact that the road isn't finished. The lanes you will need to see aren't there yet.

    I'm not explaining this very well. Right now you are looking to the right to see a NB vehicle in what will eventually be the southbound lane. When the road is finished you will be looking across another 20' to see the NB lanes. That changes the angle and explains why the sight lines will be OK. (If they aren't then it would have to be changed - but they will be. It's all a matter of geology, no - geography - no geometry). Trust me, what could possibly go wrong?

  3. I fully understand the geography/geometry thing but that does not take into account the bad driving habits of most Madison area drivers. being that the safe zone needed to enter into traffic at an intersection is left up to the driver, usually far less than sanely appropriate, giving them a rock to hide behind before doing it is even more insane. There is also the issue of being able to see vehicles pulling into the street from driveways on the same side which requires blocking the crosswalk, not rationally acceptable.
    I don't know what fresh thinking individual came up with this idea but one would think that there were others experienced with proactive accident prevention, whereby going by the numbers is not rational, would have pointed out these and other problems out long before anything was built.
    There are many other ways to address street names that are aesthetically pleasing and rationally acceptable, think again.
    knock them down!

  4. "I fully understand the geography/geometry thing but that does not take into account the bad driving habits of most Madison area drivers."

    Well, I hate to say it but no, you don't understand it. The necessary sight distance is calculation. You can either see far enough to make a safe decision or you can't.

    The engineers who have done the calculcations determined that a driver stopped at the appropriate place at each intersection will be able to see far enough down the street.

  5. I hate to say it Doug, but no, you don't understand. I am an engineer and fully realize that the numbers shouldn't be used in this situation. I guess in the future we will have the real numbers to go by, the increased number of accidents.
    use your head Doug, I did.

  6. "I hate to say it Doug, but no, you don't understand. I am an engineer and fully realize that the numbers shouldn't be used in this situation."

    First, I apologize for the wording I used earlier; sometimes I get in a hurry and pop off more than I mean to.

    But, now I really don't follow your comments. When you say that "the numbers shouldn't be used in this situation" what do you mean?

    Are you saying the vision triangle numbers shouldn't be used for some reason (Madison drivers are bad, as you first asserted, for example)? I don't agree if that's what you mean. The vision triangle numbers are always relevant, even if they are not the only factor to consider in creating a safe intersection.

    I also don't agree that Madison area drivers are measurably worse (or better) than drivers in other places.

    If you are saying that the vision triangle numbers shouldn't be used right now because the road isn't finished, then I agree. Although that doesn't make address the poor vision situation (esp. at Owen Road) in the mean time.

    What kind of engineer, by the way? I'm a lawyer, but you wouldn't want me doing your estate plan. And in my day job I am a consumer, if you will, of large amounts of engineering services related to highway safety. I've seen good, bad, and indifferent.

    I still go back to the fact that the design engineers determined that the sight distance will be adequate when the road is finished. If they are wrong, then in my opinion, the sight obstructions will have to be moved at their cost.

    Finally, the Monona Drive / Owen Road intersection will have traffic lights.

  7. To "T. Ignite" and others,

    If you call me "Dougo", your comment will not be posted. Using insults will also do the trick.