Sunday, January 25, 2015

DelDOT drifts off spec with Newark's first rumble strips

"Bicycle-friendly" rumble strips that showed up recently along Route 4 in Newark are the correct width and depth to accommodate bicycling. They have the proper escape breaks to allow entering and exiting the shoulder as needed. But as we've come to expect so often with DelDOT, critical parameters were ignored or somehow missed. In this case, the offset from the white line is double the 6" specified in the drawings, that advocates hoped would put an end to this issue once and for all. To make matters worse, there was no sweeping of the resultant debris, leaving the remaining shoulder space a hazard in several places.

The latest round of Rumble Strips, found here along Route 4 in Newark near the University of Delaware, have an offset of 2x what is specified in DelDOT's newly adopted Bicycle-Friendly Rumble Strips guidelines.

As described above, the design of the rumble strip itself is critical. But when it comes to safety, its position relative to the lane is at least as important - if not more important. Bicyclists will still prefer to ride in the shoulder, behind the rumble strip. But the more offset it is from the white line, the less debris-free space remains. This will prompt more experienced bicyclists to ride in the offset, or take part of the lane (or the whole lane in this case) instead, to avoid tire puncture or loss of vehicle control.

Edge line rumble strips, or "rumble stripes" are the overwhelming
favorite among recreation and transportation bicyclists. The above
photo was taken in rural Pennsylvania.
It is not clear why DelDOT keeps insisting on such a large offset - in this case, a foot or more. By the time a motorist senses contact with the rumble strip, they are well off into the shoulder and could be on their way to striking a bicyclist or other non-motorized user (pedestrians often walk in shoulders when no sidewalk is present). Some DelDOT officials have mentioned that edge-line rumble strips generate greater noise from more frequent contact, and thus, are disturbing to nearby housing developments. This is difficult to rationalize, however, given America's penchant for fake vehicle noise. Delaware's roads are disturbingly loud now, given what seems like every other vehicle having some type of illegal exhaust system. The police rarely - if ever enforce such noise, fines barely register, and it's not something people really complain about or it would be a recognized issue.

In summary, we again thank DelDOT for revising the guidelines and giving us a much safer rumble strip. This is critical should bicyclists unintentionally ride into one, or need to exit the shoulder for any number of reasons. But we will not stop advocating that they sharply reduce or eliminate the offset, thus maximizing safe available shoulder space. To achieve compromise, the only thing we ask is that they follow the guidelines set forth in their newly released rumble strip design guidance, as they did here on Route 896 south of the C&D Canal.


  1. I really wonder how many crashes these things prevent, or does it allow more people to drive distracted only to be nudged back onto the road when they've been texting. All the while they make cycling ever more hazardous! Thank heavens NJDOT only allows these things on limited access freeways!

  2. Rumble strips on anything less than limited access, or long straight rural roads is not going to improve safety. This particular stretch has red lights, left turning lanes, right turning lanes, the college stadium right there, etc. So I totally agree, it is almost like they are awarding deadly behavior by installing a "texting alarm" instead of upping the penalties and enforcing the law. You have to be well into the shoulder, already within striking range of a debris-avoiding bicyclist before it even sounds, eliminating any advantage as a (somewhat) protected bike lane. So yes, the strip design itself is a big improvement, but placement relative to the lane is even more important.


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