Stop Being Broken

Traffic Prompts

Tuesday, 26th February 2008

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The pressure lines that activate a traffic light often encourage you to break the law, and maybe even drive dangerously.

Intro music from the song “Drive” by Jonathan Coulton

Traffic Prompts: Should they be behind the "stop here" line? (Comments are welcome!)

• Yes
• No

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• 

Tags: cars, driving, stoplight, traffic

6 Comments to “Traffic Prompts”

1. M-D says:

   26 February 2008 at 9:11 pm

   See, here’s the problem with the logic on this one – in many cases, the ground sensors aren’t actually there to trigger the traffic light, but to monitor traffic patterns, in which case the sensor is actually OK right where it is.

   This same type of ground sensor is used on the New Jersey Turnpike near the ‘mixing bowl’ at exit 14 to monitor traffic conditions and traffic delays.

   Reply
2. JT says:

   27 February 2008 at 12:04 am

   I got curious about this myself, and it seems they are not actually pressure plates, but instead inductive loops instead. Go figure.

   MD’s comment is valid though, depends on the intent of why they are there, but it would be nice for that data to be able to collected, AND to control the traffic lights in less populated areas and or times of the day.

   Here is site of which I found out the information on the inductive loops info. Thanks for bringing intelligent thought on things we otherwise might not notice otherwise.

   http://auto.howstuffworks.com/question234.htm

   Reply
3. Bryan says:

   27 February 2008 at 8:49 am

   Sure, but if the sensors are there to monitor traffic patterns, placing them farther back behind the white stop line wouldn’t change any of the data.

   JT, thanks for the link, that was insightful!

   Reply
4. Trevor Sky says:

   27 February 2008 at 11:27 am

   It occurs to me that there is another possibility for this particular sensor: to keep the light green.

   I can imagine a situation where two lights in a row can cause a potential grid-lock due to idiot drivers who don’t wait for a clearing before entering the intersection.

   In this case, the sensor would be able to recognize the presence of a vehicle in the intersection, and possibly extend the length of the green to allow the grid-lock to clear out before giving the cross traffic its green.

   Reply
5. Jared says:

   27 February 2008 at 6:26 pm

   Huh, I always thought those loops (that’s what the toll authority calls them) were magnetic. Perhaps the extension of the loops far beyond where your car should be is a way of “bulletproofing” the design, but it’s more likely that the people installing the loops don’t care about accuracy. :)

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6. Jeff L says:

   25 May 2009 at 10:11 am

   It could be that they are there for two reasons. To collect traffic data AND to turn the light green when a car is waiting.

   Moving the sensors back behind the white line would absolutely change the data collected however, as they’d no longer be able to gather data on the amount of people running red lights (which, whether they ARE or not, they certainly CAN with the current sensor placement).

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