I don’t know “Mr. A,” so I won’t use his name. Perhaps he wouldn’t object, but I don’t know.
Anyway, I’ve complained before on this blog about the nature of traffic control in Cedar Rapids—how some intersections, especially F and Collins Road, are necessary for bike traffic, but designed strictly for auto use.
Well, rather than moan on his blog, our hero Mr. A e-mailed a well-articulated note to the city government. Here is part of that e-mail:
“I've been riding my bicycle to work and find that the best route crosses Collins Road at F-Ave NE. However, this traffic light appears to be activated ONLY by cars.
“Further compounding the issue is that when one side of F-Ave cycles green, the other side won't turn green unless a car is there as well. This often results in my ‘tailgating’ the green light on the opposite side or turning me into a pedestrian ‘dodging’ traffic holes - neither of which is safe.
“What can either of us do to make crossing Collins road safer and easier when not in a car?”
Well. Last week, as I wrote previously, I heard from another biker that a city crew had been working on the traffic sensor as Collins and F. I assume the other biker wasn’t our hero Mr. A, because he had to chat with the city crew to find out what was going on, but after the encounter, I e-mailed the city an inquiry to find out if, indeed, the rumor that the sensor had been adjusted was true.
Enter Cal Brown, a “Traffic Signal Tech II,” who e-mailed me back, and who included a nicely crafted response to questions I had posed, as well as copies of previous e-mails related to the traffic sensor.
Long story short—yes, the rumor is true. The city has adjusted the far right, far forward magnetic traffic sensors at the corner of F and Collins, headed both north and south, so that they are more sensitive and likely to pick up a bicycle.
It’s not necessarily a cure-all. Composite bikes, make of carbon-based materials, might not have a lot of iron in them and might not change the magnetic field—but then again, they do have nice steel cogs, so they might. I am lucky enough ride a heavier metal bike, and recent experimentation suggests that the sensor indeed detects my bicycle.
Well, blog fans, let’s pause here and say “thank you” to both Mr. A, and Cal Brown, for quickly making this key intersection safer for bikers.
I also raised the issue of the intersection of F and Old Marion Road, and it sounds as if Cal will look into it as soon as he can. Again, thanks. I’m glad the city of Cedar Rapids is so responsive to citizen needs. Kudos.
My one minor asterisk is that the far right lane, headed south on F at Collins, is signed as a “right turn only” lane. Not to quibble, but wouldn’t the far forward detector in the next-to-right lane, where a bike that is going South and not turning right on Collins (and heaven help any crazy biker who is turning right on Collins) would normally stop be the one to set to detect bikes?
Still, I’m happy. The street “sees” me. And I have a pretty well-written summary of what was done at the intersection, and how it works, courtesy of Cal Brown. His text is numbered because he is replying to my three questions, so, first, an excerpt from my e-mail that lists my questions, then the text of Mr. Brown’s answer with “Mr. A’s” name redacted:
My questions in excerpt from e-mail:I’ve complained in my blog before about traffic controls in the city being strictly designed for cars, and I would like to compliment the city if indeed it has changed the F and Collins traffic light triggers, and if it’s planning to put these at other intersections. I have several questions, which I assume you probably can’t answer but might be able to tell me who could:
1) Is this rumor indeed true, that is, have the traffic controls been changed at F and Collins in the way described—far forward, far right squares in the pavement designed to detect bikes?
2) If “yes,” are there other intersections where the city has changed traffic controls to aid biking? I ask because if a road detector has been adjusted to “read” bikes, a biker would need to know that because you’d still have to stop in the right spot to trigger the device, and I’m curious where else these bike detectors, if they exist, might be.
3) Again, if I’m not wrong about the whole premise—that street traffic controls have been changed to detect bikes—can someone briefly explain how car and/or bike pavement detection devices work in the first place? Are they magnetic or weight triggered? Do you merely have to cross one to trigger it or do you have to come to rest on it for a period of time—is it triggered if you’re next to the visible cut in the pavement or do you have to be on the rectangle?
Now, Cal Brown, Traffic Signal Tech II, answers (material in parentheses is my commentary, not Mr. Brown’s words):
"Gina Weaver (city employee I had e-mailed) forwarded your email regarding bicycle detection to me for clarification. Last month I responded to a question from a cyclist regarding the vehicle detectors at F Ave & Collins Rd NE. I have copied both the original request and my response at the bottom of this message. I hope that helps clarify what the cyclist you encountered was talking about. Now I will answer your specific questions.
"1. I attempted to adjust the sensitivity of the individual loop detectors in response to a specific request for that intersection. As I informed (original name removed, Mr. A) below, I “tweaked” the sensitivity in hopes that it would pick up what little metal may be on his bicycle. He later informed us that it did indeed work.
"2. We have not made a special effort to accommodate bicycles except when a specific request such as this has come in. (I expect bikers to be able to “share the road” on quiet streets anyway, without any special efforts—but some intersections like this require special care, which the city seems very willing to provide.) We do attempt to make the vehicle detectors as sensitive as we can in order to pick up any vehicle from bicycles up to high bed trucks. I am, however, forwarding this email on to Ron Griffith – Senior Traffic Engineer. He is involved quite a bit with efforts to make our streets more bicycle friendly so he may know about future plans that I am not.
"3. Now a brief tutorial of traffic signal vehicle detection. We use primarily 3 types of vehicle detection in Cedar Rapids, video cameras (NOT red light cameras), inductive loops, and wireless detection.
"a. Cameras--These are tubular camera units mounted on the traffic signal pole across the street from an approach.
"b. Inductive loops— This method has been used for several years and most of our intersections use these. A slot is sawed into the street and several turns of wire are laid in the slot creating a loop of wire in the pavement. This creates a magnetic field in the street at that point and any metal passing through that field causes a change in the magnetic field. That change is sensed by a detection unit in the control cabinet and a “call” is placed in the controller.
"c. Wireless sensors—this is a new type of technology we are working with and have been using successfully for a couple of years now. A 4” diameter hole is drilled in the pavement and a plastic “puck” is placed in the hole. This puck acts like an inductive loop where a change in the magnetic field is sensed and a call placed into the controller.
"Weight does not trigger the call, the change in the magnetic field does. When we increase the sensitivity of a detector unit, it means that a smaller change is required to send a call to the traffic controller. It’s not as simple as just “cranking up” the sensitivity to maximum so we can pick up everyone. We have to prevent “false calls” from traffic going the other direction or other undesirable things that may affect the magnetic field of the loop. The corners are considered the most sensitive part of an inductive loop because there is more magnetic field to disrupt. In most cases the vehicle needs to stay on the detector so the call is constantly sent into the controller unit.
"I hope this provides the information you were looking for. Please let us know if we can be of further assistance."
Traffic Signal Tech II
City of Cedar Rapids Traffic Engineering
1201 6th St SW