# How are no passing zones determined? **URL:** \ **Category:** Factual Questions\ **Created:** [June 16, 2016, 2:40pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527 "2016-06-16T14:40:43Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![What\_the](https://avatars.discourse-cdn.com/v4/letter/w/f4b2a3/32.png) [@What\_the](https://boards.straightdope.com/u/What_the)\ **Post date:** [June 16, 2016, 2:40pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/1 "2016-06-16T14:40:43Z")
Is it scientific to any degree or is it mainly a gut feel by whoever is responsible? To the extent that they are determined logically I’m curious about certain factors… 1. Whether the passer is expected to be tail-gating or a safe distance back of the passee when starting the process? 2. How fast is the passer expected to drive ? … and from an enforcement standpoint, how fast is he allowed to go? 3. Is it assumed the passee is doing less than the speed limit or is it acknowledged that passers should be able to drive faster than the posted speed limit? Bonus question… when passing a slow-moving vehicle like a farm implement, is it ok to pass in a no passing zone? ---
**Author:** ![Procrustus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/procrustus/32/2994_2.png) [@Procrustus](https://boards.straightdope.com/u/Procrustus)\ **Post date:** [June 16, 2016, 2:46pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/2 "2016-06-16T14:46:53Z")
> [@](#): > > Table 3B-1. Minimum Passing Sight Distances for No-Passing Zone Markings 85th-Percentile or Posted or Statutory Speed Limit > Minimum Passing Sight Distance > 25 mph 400 feet > 30 mph 500 feet > 35 mph 550 feet > 40 mph 600 feet > 45 mph 700 feet > 50 mph 800 feet > 55 mph 900 feet > 60 mph 1,000 feet > 65 mph 1,100 feet > 70 mph 1,200 feet read all about it [here.](http://mutcd.fhwa.dot.gov/htm/2009/part3/part3b.htm) ETA: No, I don’t think you should pass a slow tractor in a “no passing zone” ---
**Author:** ![Count\_Blucher](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@Count\_Blucher](https://boards.straightdope.com/u/Count_Blucher)\ **Post date:** [June 16, 2016, 3:03pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/3 "2016-06-16T15:03:48Z")
On a single lane (per direction) road, they are determined by a Double Yellow Solid Line. End. Of. Story. If you are tailgating Anybody, you need to pull over & check your blood pressure. If you are jogging from side-to-side from 4 inches behind them to get them to speed up, you are not fit to drive. If you are trying to pass on a one lane solid double yellow line road, either right side or left side, of the car in front of you… then you need to be pulled over and ticketed. ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [June 16, 2016, 3:08pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/4 "2016-06-16T15:08:04Z")
Short answer about how or where they are placed: Anywhere with curves or hills. As for how fast one can go when passing? A driver may not legally exceed the speed limit when passing. I would guess it is NEVER okay to pass anything in a No Passing zone. ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [June 16, 2016, 3:09pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/5 "2016-06-16T15:09:59Z")
> [@What\_the](#): > > 1. Whether the passer is expected to be tail-gating or a safe distance back of the passee when starting the process? > > 2. How fast is the passer expected to drive ? … and from an enforcement standpoint, how fast is he allowed to go? > > 3. Is it assumed the passee is doing less than the speed limit or is it acknowledged that passers should be able to drive faster than the posted speed limit? > > Bonus question… when passing a slow-moving vehicle like a farm implement, is it ok to pass in a no passing zone? 1. safe distance 2. up to the posted speed limit and not above 3. see answer #2. Bonus: no ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [June 16, 2016, 3:13pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/6 "2016-06-16T15:13:43Z")
> [@I.Dunno](#): > > I would guess it is NEVER okay to pass anything in a No Passing zone. Don’t start with your “No Passing Zone” shit. I know what you want. You want me to get an Aston. 😃 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 16, 2016, 3:16pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/7 "2016-06-16T15:16:12Z")
> [@What\_the](#): > > Bonus question… when passing a slow-moving vehicle like a farm implement, is it ok to pass in a no passing zone? It _is_ legal to cross the double yellow line to go around an obstruction. [Some argue](http://flbikelaw.org/2009/07/passing-a-bicyclist-in-a-no-passing-zone/) that a slow bicycle counts as an obstruction. A farm equipment, perhaps not. ---
**Author:** ![Lord\_Feldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lord_feldon/32/341_2.png) [@Lord\_Feldon](https://boards.straightdope.com/u/Lord_Feldon)\ **Post date:** [June 16, 2016, 3:21pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/8 "2016-06-16T15:21:40Z")
> [@What\_the](#): > > Bonus question… when passing a slow-moving vehicle like a farm implement, is it ok to pass in a no passing zone? It probably varies by state, but in Ohio you can pass in a no-passing zone if the other vehicle is going below half of the speed limit. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [June 16, 2016, 4:35pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/9 "2016-06-16T16:35:01Z")
> [@Omar\_Little](#): > > 1. up to the posted speed limit and not above That seems problematic. Say the car in front of you is going 10 below. Yeah, you can accelerate and then pass him at exactly the speed limit, but the longer you linger in the other lane, the more dangerous things become (and not just from oncoming traffic). I say get the pass over with as prudently and safely as possible; if they want to ticket me for passing him in 5 seconds at 10 over, vs. 10 seconds at the speed limit-I doubt there are many cops in the country that would do so. Back to the OP-I have a number of local 2 lane roads with significant straight and clear stretches which have solid double lines all the way down, but do have a lot of side streets, which is why I’d guess there are no single dashed ones. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [June 16, 2016, 5:00pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/10 "2016-06-16T17:00:00Z")
When I got a permit in Switzerland (it has no expiration date, so I guess it is still valid) the rules of the road were very explicit that it is always legal (when safe) to pass a vehicle going less than, IIRC, 20 kph. An obstacle or a bicycle is always okay as is a slow moving farm vehicle. I have no idea of any other jurisdiction. Trouble is, if it is not written that way, then it may depend on whether the cop had a fight with his wife that morning. ---
**Author:** ![What\_the](https://avatars.discourse-cdn.com/v4/letter/w/f4b2a3/32.png) [@What\_the](https://boards.straightdope.com/u/What_the)\ **Post date:** [June 17, 2016, 11:20am UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/11 "2016-06-17T11:20:22Z")
> [@Procrustus](#): > > read all about it [here.](http://mutcd.fhwa.dot.gov/htm/2009/part3/part3b.htm) > > ETA: No, I don’t think you should pass a slow tractor in a “no passing zone” Thank-you! From your link that table is.explained as follows: “On roadways with center line markings, no-passing zone markings shall be used at horizontal or vertical curves where the passing sight distance is less than the minimum shown in Table 3B-1 for the 85th-percentile speed or the posted or statutory speed limit. The passing sight distance on a vertical curve is the distance at which an object 3.5 feet above the pavement surface can be seen from a point 3.5 feet above the pavement” I see that a hill or a dip is referred to as a “vertical curve”. Do you know what 85th percentile speed refers to? Still the assumptions to the factors I laid out aren’t mentioned. Here’s another factor…Is potential oncoming traffic expected to be driving the speed limit or is there extra room to provide fore someone driving (5mph maybe) over the limit? ---
**Author:** ![What\_the](https://avatars.discourse-cdn.com/v4/letter/w/f4b2a3/32.png) [@What\_the](https://boards.straightdope.com/u/What_the)\ **Post date:** [June 17, 2016, 11:27am UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/12 "2016-06-17T11:27:37Z")
> [@Count\_Blucher](#): > > On a single lane (per direction) road, they are determined by a Double Yellow Solid Line. > > End. Of. Story. > > If you are tailgating Anybody, you need to pull over & check your blood pressure. > If you are jogging from side-to-side from 4 inches behind them to get them to speed up, you are not fit to drive. > If you are trying to pass on a one lane solid double yellow line road, either right side or left side, of the car in front of you… then you need to be pulled over and ticketed. From your location I see that this issues is dear to your heart. I pretty much agree with your sentiments but when I was referring to tailgating I wasn’t referring to riding someone’s bumper continuously. I was referring to the starting point at which the passing process begins. Perhaps a car length for every 10 mph has been factored into those tables. A comparable distance would have to be considered when it is safe to pull back into your lane as well. ---
**Author:** ![What\_the](https://avatars.discourse-cdn.com/v4/letter/w/f4b2a3/32.png) [@What\_the](https://boards.straightdope.com/u/What_the)\ **Post date:** [June 17, 2016, 11:36am UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/13 "2016-06-17T11:36:17Z")
> [@John\_DiFool](#): > > That seems problematic. Say the car in front of you is going 10 below. Yeah, you can accelerate and then pass him at exactly the speed limit, but the longer you linger in the other lane, the more dangerous things become (and not just from oncoming traffic). I say get the pass over with as prudently and safely as possible; if they want to ticket me for passing him in 5 seconds at 10 over, vs. 10 seconds at the speed limit-I doubt there are many cops in the country that would do so. > > Back to the OP-I have a number of local 2 lane roads with significant straight and clear stretches which have solid double lines all the way down, but do have a lot of side streets, which is why I’d guess there are no single dashed ones. Depending on how fas the other guy is going, it seems like it would take take significantly more than twice as long to pass at 65 vs 55. I agree with you that the powers that be do accept the passer will be speeding in order to pass someone even if the passee is doing 2-3 miles under the limit. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 17, 2016, 11:37am UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/14 "2016-06-17T11:37:18Z")
> [@What\_the](#): > > From your location I see that this issues is dear to your heart. > > I pretty much agree with your sentiments but when I was referring to tailgating I wasn’t referring to riding someone’s bumper continuously. I was referring to the starting point at which the passing process begins. Perhaps a car length for every 10 mph has been factored into those tables. A comparable distance would have to be considered when it is safe to pull back into your lane as well. If you sit back a bit from the car in front you can see more of the road ahead because the car in front is taking up a smaller angle of your vision, you can also get up to your passing speed while still in your lane then pull out for the passing manoeuvre meaning you spend less time in the other lane. Point being, there is often no benefit to tailgating prior to passing. As far as slow moving traffic goes, best to read the specific laws for your state and country. In South Australia it is legal to cross a no-passing line to pass a bicycle for example (provided you judge it to be safe.) ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [June 17, 2016, 12:40pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/15 "2016-06-17T12:40:15Z")
It was only in 2005 that Maine made it illegal to pass a motor vehicle on a double yellow line. I was surprised because I had assumed it was already illegal, but before 2005 it was only a guideline. I suppose there may still be states where the no-passing rule is only a guideline and not a law. There is no exception for passing slow farm implements in Maine. It is still legal to pass a bicycle on a double yellow line but “only when it is safe to do so.” ---
**Author:** ![SpeedwayRyan](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@SpeedwayRyan](https://boards.straightdope.com/u/SpeedwayRyan)\ **Post date:** [June 17, 2016, 12:44pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/16 "2016-06-17T12:44:23Z")
Re: speed, in a safe passing zone, I’m gonna go as fast as I feel necessary to pass someone, regardless of the speed limit. Driving in the lane generally reserved for oncoming traffic is something I’d like to minimize my exposure to while getting around someone. I’d rather risk a ticket than hang out over there twice as long in an effort to avoid one. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 17, 2016, 12:48pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/17 "2016-06-17T12:48:04Z")
> [@What\_the](#): > > I pretty much agree with your sentiments but when I was referring to tailgating I wasn’t referring to riding someone’s bumper continuously. I was referring to the starting point at which the passing process begins. Perhaps a car length for every 10 mph has been factored into those tables. A comparable distance would have to be considered when it is safe to pull back into your lane as well. I don’t see how it makes any difference. If it’s unsafe to follow a car at 100 ft distance, it’s equally unsafe to get up to 100 ft of the car in front before changing lanes for passing. ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [June 17, 2016, 1:28pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/18 "2016-06-17T13:28:22Z")
> [@SpeedwayRyan](#): > > I’m gonna go as fast as I feel necessary to pass someone, regardless of the speed limit. Great username / post combo. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [June 17, 2016, 2:09pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/19 "2016-06-17T14:09:18Z")
> [@Lord\_Feldon](#): > > It probably varies by state, but in Ohio you can pass in a no-passing zone if the other vehicle is going below half of the speed limit. > [@Hari\_Seldon](#): > > When I got a permit in Switzerland (it has no expiration date, so I guess it is still valid) the rules of the road were very explicit that it is always legal (when safe) to pass a vehicle going less than, IIRC, 20 kph. An obstacle or a bicycle is always okay as is a slow moving farm vehicle. I have no idea of any other jurisdiction. Trouble is, if it is not written that way, then it may depend on whether the cop had a fight with his wife that morning. Presumably these exceptions are applicable only when passing can be accomplished safely. On a twisting road with short sightlines, passing even the slowest object might not be a permissible option. ---
**Author:** ![somepumpkin](https://avatars.discourse-cdn.com/v4/letter/s/7feea3/32.png) [@somepumpkin](https://boards.straightdope.com/u/somepumpkin)\ **Post date:** [June 17, 2016, 2:15pm UTC](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527/20 "2016-06-17T14:15:43Z")
Since the question has been factually answered, let me tackle the bonus question with nothing even close to a substantive answer. Those lines are for stupid people with slow cars. But it’s not just about sight distance ahead, you MUST consider ingress traffic, cliffs, guardrails, etc. If you can pass safely (and I mean safely), then go for it. I take no responsibility for your tickets or scowls from other drivers. [Next page](https://boards.straightdope.com/t/how-are-no-passing-zones-determined/757527.md?page=2)