What constitutes a median or divider?

[Beltway]

OK, I didn't mean the exact same square foot.  Physically speaking, it's impossible for two vehicles to share the same space.  What I mean is that it is both legal and practicable for both directions to enter the same lane at the same time, which is exactly what the term 'divided highway' implies cannot happen.

It is not a traffic lane.  It is a left turn storage area. A prudent driver knows that he should not slam into a vehicle that is stopped there.

I know of several states (NC, VA, SC, PA) who denote such highways on their state maps as divided highways.

'Divided highway' means that there is separation between opposing traffic.

[vdeane]

In that case, any highway with a double yellow line counts.

There's an important distinction between a divided highway that people are missing: left turns are impossible except at intersections with a break in the divider.  If there's nothing but paint separating traffic, this does not occur, and the road cannot be considered divided.

[Beltway]

In that case, any highway with a double yellow line counts.

That is an undivided highway.

There's an important distinction between a divided highway that people are missing: left turns are impossible except at intersections with a break in the divider.  If there's nothing but paint separating traffic, this does not occur, and the road cannot be considered divided.

Traffic engineers believe otherwise.  A 10+ foot wide continuous flush paved divider indeed provide a divided highway.  Again, look at the legend for such highways on state highway maps.

[mightyace]

^^^
Methinks the two of you are arguing about an official definition (traffic engineers) versus a practical one (driving public).

I generally go with the practical which, in this case, is that if you can make a left turn or u-turn anywhere, then the highway is not fully divided.

[agentsteel53]

I generally go with the practical which, in this case, is that if you can make a left turn or u-turn anywhere, then the highway is not fully divided.

I can make a U-turn, quite safely, on the unpaved medians of many interstates.  I-8 between Yuma and El Centro comes to mind as having many such zones.  Indeed, one can see the tire marks, and also cops like to park in them because they can accelerate out without too much trouble.

[Beltway]

^^^
Methinks the two of you are arguing about an official definition (traffic engineers) versus a practical one (driving public).

I generally go with the practical which, in this case, is that if you can make a left turn or u-turn anywhere, then the highway is not fully divided.

I am thinking more of the rural highways, where the ability to turn left into a field entrance would be widely spaced and the likelyhood of two opposing vehicles needing to use the same left-turn space would be near the vanishing point.

[kphoger]

^^^
Methinks the two of you are arguing about an official definition (traffic engineers) versus a practical one (driving public).

I generally go with the practical which, in this case, is that if you can make a left turn or u-turn anywhere, then the highway is not fully divided.

I am thinking more of the rural highways, where the ability to turn left into a field entrance would be widely spaced and the likelyhood of two opposing vehicles needing to use the same left-turn space would be near the vanishing point.

Hmm, maybe something like US-45 between Harrisburg and Muddy, IL?  Interestingly, Rand McNally shows this as an undivided highway even though I emailed a correction to them years ago.  Of course, they still show it as undivided all the way to Eldorado, even though it has a grassy median, wide paved shoulders, and a 65 mph speed limit north of Muddy.  
http://binged.it/K3JI2G

However, the line between widely spaced and not widely spaced is a fuzzy one, so where exactly do you draw the line?  Here is an example from IL-33 between Effingham and Shumway.  It's a rural area, but housing developments are popping up along in there.  I seem to recall the speed limit being 50 or 55 mph through this stretch, but that was a few years ago.  I think it's quite reasonable to assume that opposing traffic could have a head-on while both trying to use the center turn lane.  But, other than the density of houses, there's not much difference between this one and the one north of Harrisburg.
http://binged.it/K3K2hK

[roadfro]

There's an important distinction between a divided highway that people are missing: left turns are impossible except at intersections with a break in the divider.  If there's nothing but paint separating traffic, this does not occur, and the road cannot be considered divided.

Traffic engineers believe otherwise.  A 10+ foot wide continuous flush paved divider indeed provide a divided highway.  Again, look at the legend for such highways on state highway maps.

Traffic Engineer != Cartographer

A traffic engineer will tell you a divided highway is one where the two directions of travel are physically separated, and vehicles would not physically (or legally) be able to cross the separation or neutral area.

A cartographer or map maker may not make this distinction, and depending on the legend used on the map, may not wish to make a roadway several line types if the characteristics of the road change in order to make the final product easier for the user to comprehend.

[agentsteel53]

why do cartographers place so much importance on divided highways?  I'd rather know if it was multiple lanes in the same direction, and also if the mainline is ever required to stop.  mapmakers show arterials (lots of traffic lights) the same way as expressways (no stops on the mainline, the occasional left turn and driveway access) and I certainly know which one I'd rather take...

but they make the distinction between four-lane divided, and four-lane undivided, which I don't care about in the slightest.

[kkt]

why do cartographers place so much importance on divided highways?  I'd rather know if it was multiple lanes in the same direction, and also if the mainline is ever required to stop.  mapmakers show arterials (lots of traffic lights) the same way as expressways (no stops on the mainline, the occasional left turn and driveway access) and I certainly know which one I'd rather take...

but they make the distinction between four-lane divided, and four-lane undivided, which I don't care about in the slightest.

Maybe because you can see if the highway is divided from an aerial photograph, but seeing if there are stop signs would require driving it.

[agentsteel53]

Maybe because you can see if the highway is divided from an aerial photograph, but seeing if there are stop signs would require driving it.

or you can just zoom in one level more.  striping of the road shows fairly obviously where the stop lines are.

[Beltway]

OK, I didn't mean the exact same square foot.  Physically speaking, it's impossible for two vehicles to share the same space.  What I mean is that it is both legal and practicable for both directions to enter the same lane at the same time, which is exactly what the term 'divided highway' implies cannot happen.

That's only your opinion.  It's not a traffic lane.  Look at it as a paved left shoulder that is 10+ feet wide

[Beltway]

Traffic engineers believe otherwise.  A 10+ foot wide continuous flush paved divider indeed provide a divided highway.  Again, look at the legend for such highways on state highway maps.

Traffic Engineer != Cartographer

They get the design definitions from traffic engineers.

A traffic engineer will tell you a divided highway is one where the two directions of travel are physically separated, and vehicles would not physically (or legally) be able to cross the separation or neutral area.

Unless there is a median barrier, it will be physically possible to cross the median.

If the median has crossovers, there will be places where vehicles will be able to cross the median.  It would be physically possible for 2 vehicles to collide head-on in the crossover.

[roadman65]

Traffic engineers believe otherwise.  A 10+ foot wide continuous flush paved divider indeed provide a divided highway.  Again, look at the legend for such highways on state highway maps.

Traffic Engineer != Cartographer

They get the design definitions from traffic engineers.

A traffic engineer will tell you a divided highway is one where the two directions of travel are physically separated, and vehicles would not physically (or legally) be able to cross the separation or neutral area.

Unless there is a median barrier, it will be physically possible to cross the median.

If the median has crossovers, there will be places where vehicles will be able to cross the median.  It would be physically possible for 2 vehicles to collide head-on in the crossover.

That is very interesting considering that School bus laws in Florida consider a center turn suicide lane as a median, so vehicles on the opposite side of the lane are exempt from stopping for the bus.

I also remember that many map makers showed US 17, 92, and 441  throughout most of Orlando as being divided when most is not.  Before the section from Taft- Vineland Road to Osceola Parkway was widened to six lanes and the grass median added, it had a three foot paved buffer in between the two directions of travel.  No turn lane then, just an area not designated for travel and more of just a cushion than anything.  Still from Taft- Vineland Road to Oak Ridge Road it is undivided and shown as divided.

[kphoger]

OK, I didn't mean the exact same square foot.  Physically speaking, it's impossible for two vehicles to share the same space.  What I mean is that it is both legal and practicable for both directions to enter the same lane at the same time, which is exactly what the term 'divided highway' implies cannot happen.

That's only your opinion.  It's not a traffic lane.  Look at it as a paved left shoulder that is 10+ feet wide

Then I guess I'll start looking at the few inches between parallel solid yellow lines as a paved left shoulder.  Unless there's some magic number between zero and ten feet that suddenly turns an undivided highway into a divided highway, that is.

[roadman65]

It all up to interpertation as map makers do not know the conditions. 

Look at US 209 between i-80 and PA 33 near Stroudsburg, PA?  All maps show it as a freeway, yet it is only a limited access expressway with three at grade intersections and the last time I was there in 03, two of them were signalized.  Only where it crosses its own business route is a freeway condition present as there is un-interchanged grade separation there.  That is just a few hundered feet south of I-80 where the expressway ends to be concurrent with I-80.

[NE2]

That is very interesting considering that School bus laws in Florida consider a center turn suicide lane as a median, so vehicles on the opposite side of the lane are exempt from stopping for the bus.

The fuck? No they don't. http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0300-0399/0316/Sections/0316.172.html "an unpaved space of at least 5 feet, a raised median, or a physical barrier"

[kphoger]

That is very interesting considering that School bus laws in Florida consider a center turn suicide lane as a median, so vehicles on the opposite side of the lane are exempt from stopping for the bus.

The fuck? No they don't. http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0300-0399/0316/Sections/0316.172.html "an unpaved space of at least 5 feet, a raised median, or a physical barrier"

That's as may be for Florida, but I know some states do consider a paved median to nullify the requirement to stop for an oncoming emergency vehicle and/or school bus.

[Beltway]

That's only your opinion.  It's not a traffic lane.  Look at it as a paved left shoulder that is 10+ feet wide

Then I guess I'll start looking at the few inches between parallel solid yellow lines as a paved left shoulder.  Unless there's some magic number between zero and ten feet that suddenly turns an undivided highway into a divided highway, that is.

No.  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.

[kphoger]

That's only your opinion.  It's not a traffic lane.  Look at it as a paved left shoulder that is 10+ feet wide

Then I guess I'll start looking at the few inches between parallel solid yellow lines as a paved left shoulder.  Unless there's some magic number between zero and ten feet that suddenly turns an undivided highway into a divided highway, that is.

No.  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?

[Beltway]

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.

[flowmotion]

why do cartographers place so much importance on divided highways?  I'd rather know if it was multiple lanes in the same direction, and also if the mainline is ever required to stop.  mapmakers show arterials (lots of traffic lights) the same way as expressways (no stops on the mainline, the occasional left turn and driveway access) and I certainly know which one I'd rather take...

but they make the distinction between four-lane divided, and four-lane undivided, which I don't care about in the slightest.

True, it's especially annoying when parkways (slow speed landscaped roads) are marked as divided highways simply because there's a median.

[vdeane]

why do cartographers place so much importance on divided highways?  I'd rather know if it was multiple lanes in the same direction, and also if the mainline is ever required to stop.  mapmakers show arterials (lots of traffic lights) the same way as expressways (no stops on the mainline, the occasional left turn and driveway access) and I certainly know which one I'd rather take...

It kinda makes a big difference if you need to make a left turn into a house or business.

[Beltway]

why do cartographers place so much importance on divided highways?  I'd rather know if it was multiple lanes in the same direction, and also if the mainline is ever required to stop.  mapmakers show arterials (lots of traffic lights) the same way as expressways (no stops on the mainline, the occasional left turn and driveway access) and I certainly know which one I'd rather take...

It kinda makes a big difference if you need to make a left turn into a house or business.

Yes, and also the difference between standing in the left lane behind you, and not standing in the left lane behind you.  BIG difference...

[vdeane]

If you can't make a turn because something is divided, you have to alter your route.  Not "want to" alter your route, HAVE TO.

How would you feel if maps worked the way you want them to, you planned a route based on one, only to find that the place you're going to is on the left side of a divided highway and you can't turn into it's driveway, thereby having to navigate your way around local streets you never planned to go on to find a place to turn around and get on the other side?  These days you can check in Google (for the most part; some areas have no street view with blurry satellite imagery), but that wasn't always the case.