Very Frequent Accidents at Traffic Shifts on I-35E Project in Dallas area

[Brian556]

There are several traffic shift throughout the project. However, very frequent accidents occur at certain ones.

There is one at Whitlock Lane nearly every day.

The Lewisville Lake bridge shifts also have very frequent accidents. There were two in the northbound direction in the same day yesterday.

The rate of accidents at these locations is utterly ridiculous, and, in my opinion, indicates the presence of unsafe conditions.

I think the following conditions at shift contribute to accident rates:
1. Lack of Chevrons.
2. Insufficient warning for drivers in middle lanes
2. Shifts too sharp.
3. Lanes too narrow.

I have always though that additional safety measures need to be required at traffic shifts.
1. Chevrons are needed, and should be required.

2. Cable-strung overhead warning signs should be required for multi-lane shifts where you cannot have one side-mounted sign per lane.
This is because drivers in middle lanes often cannot see warning signs due to large vehicles in the outside lanes.

Traffic shift represent the most hazardous conditions in freeway work zones, and safety standards for them really need to improve.

[Alps]

A properly designed shift, at an S:1 or greater taper (S = prevailing speed), without narrow lanes - this would satisfy the second point #2 and point #3 - would not have a greater accident rate. Chevrons and overhead signs are completely unnecessary in a lane shift, and only serve to clutter the necessary information. The most you need to do is delineate barriers.

[dfwmapper]

I haven't been on that part of 35E in a while, but if it's anything like the ones on LBJ, one of the biggest factors is determining where the actual lane markings are. On sections that have been shifted around a few times, there might be 4 or 5 different sets of markings, and they do a shitty job of scraping off the old ones so it's really hard to tell them apart under low light conditions, especially if the roads are wet. Other than that, I'd say it's mostly human error: driving too fast and not paying enough attention.

[jeffandnicole]

While you are calling for chevrons, if the problem is in the middle lanes and those drivers can't see signs as you noted, the chevrons won't make a difference.

And is it officially noted there's an increase in accidents, or is that an estimation based on what you have seen during the moment you drive thru there?  There's a very big difference between the 2, as maybe you just happen to catch a few accidents while you drove thru that area. Accidents could even be reduced other times during the day.

[WichitaRoads]

Let's move this to the proper forum in National Boards, shall we?

ICTRds

[Brian556]

I came up on an accident that have just happened several days ago. It was NB at the beginning of the Lake Bridge shift. A car in the left lane had struck the beginning of the barrier.

I drove this section today, and noticed that there was only one warring sign on the right side of the road for this shift. The driver in the left lane could easily have not been able to see it.

The median is a little narrow here, so a typical 48 x 48 diamond would barely not fit. However, they could make a custom rectangular/square sign that would fit. This practice is common in elsewhere; I think Atlanta and/or Nashville.

Having only one warning sign for three lanes is very inadequate. A truck in the right lane could hide it from drivers in the center and left lanes.

This shift does appear to be properly designed, and not too sharp. The lane lines are broken, but are solid at other shifts. Solid lines provide better delineation, and a good visual cue that a shift is present.


As for the Whitlock Lane problem area, I haven't been through there in a while. But, accidents are reported there very frequently. Way more than before construction started.

[roadfro]

I drove this section today, and noticed that there was only one warring sign on the right side of the road for this shift. The driver in the left lane could easily have not been able to see it.

The median is a little narrow here, so a typical 48 x 48 diamond would barely not fit. However, they could make a custom rectangular/square sign that would fit. This practice is common in elsewhere; I think Atlanta and/or Nashville.

Having only one warning sign for three lanes is very inadequate. A truck in the right lane could hide it from drivers in the center and left lanes.

On some NDOT projects with similar conditions (narrow left shoulder on barrier-separated divided highway), they will do a couple things to warn about the lane shifts:
* A portable VMS supplements signage, so there's a couple warnings for drivers to see.
* Also, they'll sometimes use a 36" warning sign post-mounted on the median wall at a higher-than-normal height. This is high enough to be over most passenger cars to help avoid accidental hits, and provides a standard warning sign on both sides of the roadway.