Originally Posted by
bshanteau
Not for bicycles, no. There is new language in the
California Manual on Uniform Traffic Control Devices that, for all new detector installations, bicycles that are anywhere in the "limit line detection zone", which is a 6'x6' square with its front edge at the limit line, need to be detected.
The only loop configurations that can detect bicycles are diagonal quadrupoles, such as a Caltrans Type D (which was invented by 3M in the 1980's) or a quadracircle (which was invented in Palo Alto in about 1990).
You need to look to see if you can tell which loop is the newest. Look closely at the loop sealant covering the slots. You may be able to see a continuous strip of loop sealant in one direction or the other.
I don't see the photo attached to your original post any more, but when I looked at it a few days ago I couldn't see enough detail to tell which strip of loop sealant was continuous. You may be able to tell in person.
By the way, you may want to look at my
FAQ entry at traffic loops for the rec.bicycles archive.
That is largely the problem... as the street wears and gets dirty, it is difficult to tell which loop is newer or active.
The photo in the original post is just representative of what I see from time to time... and this is on regular residential streets. Newer streets with BL do have loops in the BL. But I live in a 60 year old neighborhood.
Fortunately for me the traffic in this area often opens up enough for me to run the light, or a car comes along and triggers it... otherwise this would be a very very annoying problem.
