Rumble Strips and Pedestrian Safety

[civilman72]

We recently re-designed a two-lane rural/suburban road with a widened asphalt shoulder, intended to allow safer pedestrian access in the road corridor. Stripped drive lane widths are 11' with a 7'-8' paved shoulder on one-side for pedestrians/bicycles. This was previously a 28' wide asphalt road with no stripping so we have some concerns with vehicles staying in the 11' lane and potentially drifting into the paved shoulder. We've considered the use of rumble strips at the shoulder to potentially increase pedestrian and bicycle safety but have struggled to find any pertinent reports for studies on this subject. There's clearly lots of information on shoulder rumble strips and their effectiveness in decreasing run-off-road accidents, but nothing pertaining directly to pedestrian safety. Any help or guidance would be appreciated.

 

[IRstuff]

There wouldn't be much data, I would think, given that rumble strips are usually on roads where pedestrian traffic is not allowed. Nevertheless, when you compare a road with rumble strips vs. one without, even the basic run-off-road accident rate difference should hopefully show a net benefit.

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[Twinkie]

Why are you promoting pedestrian use of the shoulder?

But sticking with your topic, rumble strips are to prevent runoff accidents, they are not intended as a safety feature to protect bikes/peds.

I think you'd probably do a lot better with pavement markings and signage (Sharrows, Share the Road signs, etc)

 

[ACtrafficengr]

By providing a shoulder on one side, you're encouraging wrong-way travel of bicyclists and pedestrians. There are good reasons why people are required to walk facing traffic and ride with traffic. Why not 10 ft lanes and 4 ft shoulders on both sides? Also, as Twinkie alluded, is there a reason you can't provide standard sidewalks?

It would help if you mentioned the AADT, prevailing speed and crash history. Is there a reason you think you need more than just an edge line?

Are you asking about a crash reduction factor for pedestrian crashes, or whether rumble strips would pose a trip hazard?

I can't find it, but I recall seeing a paper on the lateral extent of lane departures with rumble strips. For drift-off excursions, it was actually quite low. I think it was around a foot, so rumble strips may improve the safety of shoulder users in this type of crash. They wouldn't help for loss of control crashes, though.

As far as tripping, football shaped rumbles would meet the ADA criterion for a maximum change in elevation of not more than 1/2"/12mm without a 45 degree angle.

 

[TerryScan]

Here is a location where there is bike & ped on the shoulder with rumble strips (This is Rt 1, part of the Federal Highway System too). I think rumble strips here are a GREAT idea here. One may also note the pavement marking they show for bike/ped.

http://tinyurl.com/h4j29zg

 

[civilman72]

Thanks for all the quick replies. To put more context to my question, this is in the Rocky Mountains and is a steep (4%-12%) road maintained by the County. But unlike 95% of the county roads this one happens to have a lot of pedestrian traffic and bicycle use, which is mixed with the highest traffic volumes of any county road (2500 AADTs). It has very steep existing side slopes (1:1-2:1, 10'-30' in height) so widening of the road surface to accommodate standard sidewalk widths and separation from the roadway is not feasible. Plus the mentality of the county (very rural in nature) is that "we plow roads, not trails." They also mentioned a potential liability if they acknowledge that they are trying to accommodate the pedestrians and bicycles, but at the same time when there's an accident on another county road they'll immediately bring up governmental immunity - very confusing to me. I had extensive meetings with the County Commissioners trying to convince them to think outside the box because of the mixed-use of this particular road and to consider a raised concrete path (4' wide) with curb and gutter, and members of the public expressed a similar sentiment and concern. The widening of the asphalt shoulder was the only compromise the Commissioners were willing to concede to address the issue, and they still directed me to not label that area as a "trail" in my design plans and use "widened shoulder" instead. So the idea of posting pedestrian safety signs on the road to further bring attention to this "trail" (excuse my French) may not be a good idea. I'm guessing many of you have been in my shoes and can relate to my frustration...

To answer a few specific questions:

Regarding rumble strips in my region, because of snow-plowing, we use depressed strips that our ground into the asphalt.

The reason I'm considering rumble strips is that the original road was much wider without striping (28'-30') so vehicular speeds were a lot higher than posted speed (25 MPH). As an attempt at traffic calming the new design includes 11' stripped driving lanes and based on previous driving habits I'm afraid a lot of vehicles will end up in the paved shoulder. Also, with snow on the ground the white edge line is hard to decipher but you can still feel the rumble strips when your tires hit them.

 

[civilman72]

Just re-read my post and I said "stripped." Ha, hope that's not too distracting...

 

[Twinkie]

Honestly, this situation doesn't sit well with me. You had high speeds on a road with minimal pavement markings. All you are doing is restriping the road, but the "perceived" road width remains unchanged. You may be dealing with some very high speeds on this road for a while into the future.

Do you have bike/ped counts?? Can you go to 5-6' with a grass separation?

This is definitely a unique situation.

Could you give a google earth location? I'm curious.

 

[IRstuff]

In addition to the rumble strips, the edge should be demarcated with those vertical plastic hollow poles that are often installed on roads. The proximity of those things to the lane will tend to make people go slower.

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[civilman72]

Twinkie: One of the options I presented to the County was a 3'-4' grass buffer with a 4' paved shoulder and was shot down. I've attached a link to the Google Earth location (hopefully it works).
IR: Those are not an option for snowplows.

 

[Twinkie]

It look like you have plenty of sight distance along this road, so I'm not as concerned as I was before, and that looks like a phenomenal road to ride too!

I think your approach is adequate, with signage and pavement markings.

It looks like there is a trail that runs parallel to this road. I can see why cyclists would want to use the road, but why the pedestrians?

 

[civilman72]

Twinkie: The trail you see is down low in the valley and doesn't have good access to the residences at the top of the hill, plus it's snow-packed for at least 6 months of the year.

Right now, the County will probably have a wait-and-see approach on the rumble strips until after the final asphalt and striping is installed and we get a better feel for driver behavior and tendencies. I wanted to do some research up-front to see if I find anything interesting.

 

[Twinkie]

There is an article in Journal of Transportation Engineering this month regarding rumble strips.

I don't have access to the current year, but maybe something useful in there.

http://ascelibrary.org/doi/abs/10.1061/(ASCE)TE.1943-5436.0000821

 

[geewiz20]

Few suggestion to consider if you haven't already (by most favorable first):
1. Jersey barrier separation to keep traffic separated from ped/bike way
2. Raised the asphalt maybe like 4 to 6 inches in the ped/bike area
3. Use traffic "Candle-sticks" along the outside of the travelway on the ped/bike lane
4. Use pavement marking to crosshatch out the area with signage to alert drivers to share the road
5. Longitudinal rumble strip crossing the roadway, in area with poor sight distances, i.e. in advance of tight curves.

In Regards to signage, consider signage
- to warn drivers to stay at the speed limit (with fine posting)
- tell bikers to get off there bike to use the area
- signage to tell drivers to share the road

Overall, anything more you can do then put down a standard white strip would be good.

I honestly don't fell comfortable with the design to have ped/bike using the same pavement area as vehicle traffic, especially there facing on coming traffic. But if ped/bike is going to use the area regardless it only helps to provide some type of traffic control device or signage. But I also understand the liability side of it, at the very least cross-hatch the area out and put speed limit restriction signage along the road.