What constitutes a median or divider?

[mcdonaat]

I would say that a divider or double line would be used for a situation when widening a highway that is going through a sensitive area (historic downtown, dense residential development) where the extra right of way cannot be bought, or wouldn't be feasible. A median would be best served where the highway is in an open area, and the highway is expected to have higher travel speeds. On US 190, the highway is a mix of undivided and divided sections between Opelousas, LA and Port Allen, LA. Speeds also differ because of the road type.

I find the difference to be that if you can cross the yellow line and not be in an opposing lane, it is divided, no matter the width of the median (raised curb or full blown freeway-size median). If you cross the yellow line and immediately are at harm of getting hit, then it is undivided. It's really a choice thing, in my opinion. I prefer divided highways in a residential area with a median of 1-2 feet (enough for foliage and landscaping), and undivided in a downtown setting.

[agentsteel53]

the amount of time wasted trying to find the next u-turn point is probably a hell of a lot less than the time wasted realizing your expressway is really an arterial with a traffic signal every 300 feet.

[roadfro]

A road with a double yellow line separating opposing traffic is the definition of an undivided highway. 

The 10+ feet flush median is the point at which a truck or bus could stop there and be out of the traffic lanes and not be blocking the left lane.  It is also 10+ feet separating opposing traffic rather than 12 inches.  A divided highway.

If the separator is narrow enough that a left turning vehicle will block the left lane, it is an undivided highway.

So the division is at 10 feet?  A 9-foot paved neutral space would make the road undivided?

I'm not claiming where the exact point is.  The maximum normally allowed width of a truck or bus is 8.5 feet.  Take it from there as to what it would need.

And that is the problem with including calling a road with a TWLTL a divided highway... There is no defined point at which there is a physical separation. A raised median, guard rail, jersey barrier, cable barrier, unpaved neutral area, landscape buffer all present the physical separation between opposing flows of traffic that is clearly not meant for vehicles to travel upon. A TWLTL, by definition of it being a turn lane, lacks separation between opposing flows of traffic, no matter how wide the turn lane is.

[Beltway]

And that is the problem with including calling a road with a TWLTL a divided highway... There is no defined point at which there is a physical separation. A raised median, guard rail, jersey barrier, cable barrier, unpaved neutral area, landscape buffer all present the physical separation between opposing flows of traffic that is clearly not meant for vehicles to travel upon. A TWLTL, by definition of it being a turn lane, lacks separation between opposing flows of traffic, no matter how wide the turn lane is.

A 10- to 12-foot paved median does indeed separate opposing traffic.  By painted lines and signs, it is clearly denoted for left turns only, that it is not a traffic lane.

As for physical separation, a grass median is not a physical barrier, and a vehicle could easily turn across it if the driver ignores the law.

The separation point at left edge of the left lane on any road is clearly defined by a painted yellow line.

[vdeane]

There is a difference between "separation" and "barrier".  A grass median is separated even though there's no barrier.

As for the expressway thing... I wouldn't know.  By your definition, NY has no expressways, and the closest stuff we've got has traffic lights etc. and were built in the last 20-30 years.

[Scott5114]

It's rather pedantic to say that someone could cross a grass median. Practically speaking, nobody does; there is usually a ditch in the center and people fear getting stuck in either that or the mud. Even people determined to cross the median will find a graded or paved crossover. Hell, Beltway, your definition on page one is so stringent it would make the Indian Nation Turnpike "undivided" (it has a grass median narrower than a turn lane with no barrier) and that's ludicrous, as it is a fully access-controlled freeway facility with a speed limit of 75 MPH.

For that matter, someone could ramp their pickup truck up on a raised median island and cross over that, too. But nobody that's not a complete asshole would try to do that.

[Kacie Jane]

A 10- to 12-foot paved median does indeed separate opposing traffic.  By painted lines and signs, it is clearly denoted for left turns only, that it is not a traffic lane.

I'm confused by this insistence that traffic turning left does not count as traffic.

[Beltway]

A 10- to 12-foot paved median does indeed separate opposing traffic.  By painted lines and signs, it is clearly denoted for left turns only, that it is not a traffic lane.

I'm confused by this insistence that traffic turning left does not count as traffic.

It is not a general purpose lane, it is only used briefly for turning traffic.

I'm confused by this insistence of a few that there is no difference between a 4-lane highway with only a double yellow paint line dividing, and a a 4-lane highway with a 12-foot paved flush median.  That is what they are saying when they assert that the latter is "undivided".

[kphoger]

I'm confused by this insistence that traffic turning left does not count as traffic.

I'm confused by this insistence of a few that there is no difference between a 4-lane highway with only a double yellow paint line dividing, and a a 4-lane highway with a 12-foot paved flush median. 

I agree that both assertions go against common sense.  But I still see no place at which to draw the proverbial line.  And, if we're talking about mapmakers here, then we need specific criteria.  'Large enough to store a left-turning vehicle' isn't good enough, unless you expect a mapmaker to drive out there, park his vehicle in the neutral space, and wait to see if anyone smacks his car into smithereens.

Is there a difference between only a double line and a 12-foot paved neutral space?  Of course.  But is there a difference between an 8-foot and a 10-foot paved neutral space?  Well, that's a little stickier.  And I'm not sure we would all feel comfortable with the 8-foot-divided road and the 10-foot-divided road being labelled differently on maps.

Another question to resolve:  Is there a difference between a paved neutral space with yellow slashes, one with occasional left-turn lanes bitten into it, and a continuous shared left-turn lane?  Common sense would tell us there is some difference, but it's up to debate whether the difference is substantial enough to warrant a distinction in (a) speed limit and (b) map symbol.

[vdeane]

I would say that there's a much greater difference between roads with a median divider and a shared left turn lane than those with a shared left turn lane and those that are undivided with only general travel lanes.

[Beltway]

I would say that there's a much greater difference between roads with a median divider and a shared left turn lane than those with a shared left turn lane and those that are undivided with only general travel lanes.

I agree.  An undivided highway means that a left turning vehicle slows and perhaps stops in the left lane before turning, which is an obvious safety issue on a 4-lane highway.  A 12-foot paved median obviates that, and in addition provides 12 feet separation between oncoming general purpose lanes.

As far as mapmakers knowing exactly how wide the paved median is, the DOT will have as-built design plans at minimum, and many have cross-section (and other pertinent) data on an inventory information system.

The FHWA and MUTCD websites don't seem to answer the issue here, as to the exact definition of a divided highway.

[NE2]

One possible solution for mapmakers is to use the number of lanes rather than whether there's a median. A rural four-lane with a center turn lane is much better than a two-lane divided, and even a four-lane with just a centerlne is better than a two-lane.

[agentsteel53]

two-lane divided

if you mean "one lane each direction", like CA-37, then that is the worst type of road out there! 

[hbelkins]

One possible solution for mapmakers is to use the number of lanes rather than whether there's a median. A rural four-lane with a center turn lane is much better than a two-lane divided, and even a four-lane with just a centerlne is better than a two-lane.

In my experience, that's generally how i've seen it done. I most often see references to multi-lane roads as opposed to divided highways. For limited-access roads, Rand McNally generally uses their typical free or toll markings but uses "two lanes" as text to distinguish between the four-or-more-lane routes those symbols usually designate.

[kphoger]

As far as mapmakers knowing exactly how wide the paved median is, the DOT will have as-built design plans at minimum, and many have cross-section (and other pertinent) data on an inventory information system.

No, we're still left with the issue of where to draw the line.  I also refer back to my not-so-hypothetical situation where a road was median-divided for most of its length, but where part of it is missing the barrier and leaving only a 1-meter gap in the center.  I say this is not so hypothetical by referring you to the following:

Grassy median http://g.co/maps/resc2
Disappears in favor of a median drainage ditch http://g.co/maps/a5rjr
Disappears in favor of paved neutral space of approx. 0.5 to 1 meter http://g.co/maps/n69r2
Gains a central barrier http://g.co/maps/ta6su
Goes back to a grassy median http://g.co/maps/ggw54

Total length of this GMSV jaunt:  less than 6 miles

[Kacie Jane]

A 10- to 12-foot paved median does indeed separate opposing traffic.  By painted lines and signs, it is clearly denoted for left turns only, that it is not a traffic lane.

I'm confused by this insistence that traffic turning left does not count as traffic.

It is not a general purpose lane, it is only used briefly for turning traffic.

I'm confused by this insistence of a few that there is no difference between a 4-lane highway with only a double yellow paint line dividing, and a a 4-lane highway with a 12-foot paved flush median.  That is what they are saying when they assert that the latter is "undivided".

A TWLTL, while certainly not a general purpose lane, is also certainly not equivalent to a true median or a shoulder.  While medians/shoulders can be used for storing turning vehicles, they're not necessarily intended to be -- they're intended to store disabled vehicles, and to provide separation (from either opposing traffic, or to provide a buffer between the roadway and the trees).  That's the exact opposite of a TWLTL, where the explicit purpose is to store turning vehicles -- actively moving traffic -- but it provides a buffer more by coincidence.

Note that I am not saying there's no difference between a four-lane road with nothing but a yellow centerline and a four-lane road with a TWLTL.  Certainly there is.  But there is also a difference between the latter and a four-lane road divided by a median/barrier that traffic is not allowed to cross.  (No comment on the side discussion of whether one is automatically better than the other.)

[Beltway]

As far as mapmakers knowing exactly how wide the paved median is, the DOT will have as-built design plans at minimum, and many have cross-section (and other pertinent) data on an inventory information system.

No, we're still left with the issue of where to draw the line.

I don't know and it's really not my issue.

Modern standards would be 12 feet, that is what I have seen in Virginia of the projects built in the last 20 years.  That is clearly wide enough to be a divided highway.  Older roads with 10 feet would be wide enough as well, as the maximum width of a truck or bus is 8.5 feet.

[Beltway]

A TWLTL, while certainly not a general purpose lane, is also certainly not equivalent to a true median or a shoulder.  While medians/shoulders can be used for storing turning vehicles, they're not necessarily intended to be -- they're intended to store disabled vehicles, and to provide separation (from either opposing traffic, or to provide a buffer between the roadway and the trees).  That's the exact opposite of a TWLTL, where the explicit purpose is to store turning vehicles -- actively moving traffic -- but it provides a buffer more by coincidence.

I've seen paved flush medians used in rural areas were there are right-of-way constrictions, where it is a median and there are only sparse places where a left turn would be possible.

Also, at a major intersection typically the lane is not "two way", it is painted to be single direction turn lane for 300 to 500 feet before the intersection.

[Kacie Jane]

It could be that I'm misunderstanding you (or you misunderstood my previous post), but I don't see how either of those statements contradict anything I said.

[roadfro]

A 10- to 12-foot paved median does indeed separate opposing traffic.  By painted lines and signs, it is clearly denoted for left turns only, that it is not a traffic lane.

I'm confused by this insistence that traffic turning left does not count as traffic.

It is not a general purpose lane, it is only used briefly for turning traffic.

I'm confused by this insistence of a few that there is no difference between a 4-lane highway with only a double yellow paint line dividing, and a a 4-lane highway with a 12-foot paved flush median.  That is what they are saying when they assert that the latter is "undivided".

A TWLTL, while certainly not a general purpose lane, is also certainly not equivalent to a true median or a shoulder.  While medians/shoulders can be used for storing turning vehicles, they're not necessarily intended to be -- they're intended to store disabled vehicles, and to provide separation (from either opposing traffic, or to provide a buffer between the roadway and the trees).  That's the exact opposite of a TWLTL, where the explicit purpose is to store turning vehicles -- actively moving traffic -- but it provides a buffer more by coincidence.

This last comment makes me realize that I think that we are confusing 'divided' with 'separated'. A TWLTL or "paved flush median" does not necessarily constitute a division or divided highway in the sense of the physical separation of opposing traffic, where a vehicle would have to cross some non-pavement surface or barrier to enter opposing travel lanes. However, a TWLTL or paved neutral area does provide a buffered separation between those opposing traffic flows that can be traversed relatively easily (whether legal or not). Both could be considered a type of 'median' though. I think it is similar to how the MUTCD defines a difference between barrier-separated and buffer-separated HOV lanes.

In any event, this distinction could possibly explain why lines on maps tend to muddy the difference...