Unquestioned · 70-79, M
SomeMichGuy · M
Yes.
1) Originally, I think that they made connecting all the "roads to cities/towns { x_j }" easy.
Before any grid-type system, most towns were seemingly built on a hub-and-spoke system, with the central square at the middle and roads heading out from there to the next towns, which could be in ANY direction.
Even after grids became more common in towns, the shortest path to "next towns" were straight lines to those towns, modulo deviations for better terrain, oxen/horses and carts, etc.
This leads to all sorts of rural intersections where roads meet at ANY angles. Turning the crossroads into a roundabout makes for a way to have a form of uniformity regardless of the angles.
The crucial difference in the UK v. where I am in the US is this:
the UK always has a sign with a "plan view" of the intersection, like you'd see on a map, showing the road names, the destinations along them, and the appropriate angles between them
That makes navigating them much easier. At some point, the roundabouts seem to have been starting points for new paths between them and other towns.
2) With automobiles, all else being equal, safety is worst when autos cross each others' paths; i.e., at intersections where one turns across other lanes of traffic. Protected turn lanes (with green arrows in the US) can help, but that induces waits for a lengthened signal program.
So roundabouts give a number of other advantages:
A) Traffic only flows in one direction, so they tend to be safer than what many view as the "standard intersections" with which they grew up--fewer accidents is good.
B) Traffic lights require programming. This programming is hard to get right for all traffic situations seen at an intersection AND inevitably introduces delays or more sensors (and sensors can be fickle and they depend upon the composition of the vehicle!). So roundabouts save
i) The cost of the lights, the supports to suspend them, and the ongoing installation and maintenance.
ii) No lights overhead means they can't become bombs in a weather event or line failure / accident involving supporting poles, etc.
iii) The programming of the lights, which may need frequent tuning, another potential initial cost and maintenance cost.
iv) The cost of sensors, including maintenance.
v) The cost of electricity for the above.
vi) Requiring that vehicles have enough magnetic material that they can trip a sensor, thus limiting advances in automotive construction.
vii) Adding new roads is relatively simple, with new signs being the only required element beyond extending the roads to intersect the roundabout.
1) Originally, I think that they made connecting all the "roads to cities/towns { x_j }" easy.
Before any grid-type system, most towns were seemingly built on a hub-and-spoke system, with the central square at the middle and roads heading out from there to the next towns, which could be in ANY direction.
Even after grids became more common in towns, the shortest path to "next towns" were straight lines to those towns, modulo deviations for better terrain, oxen/horses and carts, etc.
This leads to all sorts of rural intersections where roads meet at ANY angles. Turning the crossroads into a roundabout makes for a way to have a form of uniformity regardless of the angles.
The crucial difference in the UK v. where I am in the US is this:
the UK always has a sign with a "plan view" of the intersection, like you'd see on a map, showing the road names, the destinations along them, and the appropriate angles between them
That makes navigating them much easier. At some point, the roundabouts seem to have been starting points for new paths between them and other towns.
2) With automobiles, all else being equal, safety is worst when autos cross each others' paths; i.e., at intersections where one turns across other lanes of traffic. Protected turn lanes (with green arrows in the US) can help, but that induces waits for a lengthened signal program.
So roundabouts give a number of other advantages:
A) Traffic only flows in one direction, so they tend to be safer than what many view as the "standard intersections" with which they grew up--fewer accidents is good.
B) Traffic lights require programming. This programming is hard to get right for all traffic situations seen at an intersection AND inevitably introduces delays or more sensors (and sensors can be fickle and they depend upon the composition of the vehicle!). So roundabouts save
i) The cost of the lights, the supports to suspend them, and the ongoing installation and maintenance.
ii) No lights overhead means they can't become bombs in a weather event or line failure / accident involving supporting poles, etc.
iii) The programming of the lights, which may need frequent tuning, another potential initial cost and maintenance cost.
iv) The cost of sensors, including maintenance.
v) The cost of electricity for the above.
vi) Requiring that vehicles have enough magnetic material that they can trip a sensor, thus limiting advances in automotive construction.
vii) Adding new roads is relatively simple, with new signs being the only required element beyond extending the roads to intersect the roundabout.
LeotardWearer · 56-60, M
@SomeMichGuy Very good outline of pros & cons, thanks. Interesting that US doesn't normally have a plan view. Go Google "Magic Roundabout" in UK Hemel Hempstead or Swindon for a dose of mini roundabouts on a roundabout. Suprisingly works well once you get over the shock of the thing :-)
SomeMichGuy · M
@LeotardWearer I think getting used to them is important, yes.
Some roundabouts here have the plan view, but too few; it should be required.
The other problems I've noticed here in the US:
A) Having
too small a roundabout + only "YIELD" signs = roundabout can lock in one direction and prevent traffic flow (making it inferior to "all-way 'STOP' signs / all-way blinking red lights").
This could be fixed via
i) making the roundabouts larger (thus more costly and more maintenance), or
ii) replacing "YIELD" signs with "STOP" signs, which would also help stop the asses who
blow through them without even attempting to see who might be there.
B) Having multiple--usually two--small roundabouts so close together that they should be combined into a single "ellipseabout".
Some roundabouts here have the plan view, but too few; it should be required.
The other problems I've noticed here in the US:
A) Having
too small a roundabout + only "YIELD" signs = roundabout can lock in one direction and prevent traffic flow (making it inferior to "all-way 'STOP' signs / all-way blinking red lights").
This could be fixed via
i) making the roundabouts larger (thus more costly and more maintenance), or
ii) replacing "YIELD" signs with "STOP" signs, which would also help stop the asses who
blow through them without even attempting to see who might be there.
B) Having multiple--usually two--small roundabouts so close together that they should be combined into a single "ellipseabout".
shinyplasticlove · 51-55, M
I've seen people around here stop while going around to yield to someone trying to get on.
LeotardWearer · 56-60, M
Tracos · 51-55, M
I actually prefer them over traffic lights
TurtlePink · 22-25, F
Never go to Conway, Arkansas 🤣