Drove I-55 from St Louis to the Chicago burbs today, and wondered why they place the highway destination mileage signs where they do. They generally list 3 towns/cities along the route, but I wasn’t able to discern any clear pattern of why they place them in any one spot rather than another.
The way my mind works, I’d imagine they might place them such that at least one of the destinations was a multiple of 5 or 10 - tho I acknowledge there is no reason that is inherently better. Or maybe have them a set distance before the nearest of the 3 - 10 or 15 miles. Or count down to the biggest “target” destination by 25 miles.
But they all seemed to be random, like:
Town A 17 Miles
City B 46 Miles
City C 223 Miles
The route is pretty much cornfields, so they easily could put it a mile earlier or later.
Anyone have any insight as to how this gets decided?
I don’t know if this is the kind of answer you are looking for, but I’ve noticed they usually appear after a junction with another highway. Not usually after a state or county road, but after a state or US highway, you will generally see one.
My brother pointed this out to me decades ago when our family would take long road trips.
Road signage is controlled by national standards, andseems to be pretty solidly evidence-based.
The Australian national standards are captured in the [Austroads](file:///C:/Users/678003/Desktop/AGTM10-16-Guide-to-Traffic-Management-Part-10-Traffic-Control-and-Communication-Devices.pdf)Guide - Section 10 - which deals with road sign design and placement, among other things. Chapter 4 goes into detail. Doubtless there will be a US National and probably state standards that apply as well.
Distance to … signs are referred to as reassurance signs. As Alpha Twit notes they are placed after intersections and junctions to confirm that the driver will end up in New York rather than the Mojave Desert, and also because the roadside environment leading up to an intersection is filled up with other sorts of signs that should demand the driver’s attention.
A relevant excerpt:
‘Advance direction signs allow drivers time to select a route prior to entering an intersection. Intersection direction signs (position signs) are used to confirm the route to be taken out of an intersection, while reassurance direction signs are located beyond the intersection to reassure drivers that the correct choice has been made, and to provide distances to destinations along the route. All three types of direction sign are normally used on important roads, and advance direction and reassurance direction signs are often not provided on roads of lesser importance.’ [p. 30]
It’s similar in the US. From the Manual on Uniform Traffic Control Devices, section 2E.38:
"Guidance:
01 If space between interchanges permits, as in rural areas, and where undue repetition of messages will not occur, a fixed sequence of signs should be displayed beginning 500 feet beyond the downstream end of the acceleration lane. At this point a Route sign assembly should be installed followed by a Speed Limit sign and a Distance sign, each at a spacing of 1,000 feet.
02 If space between interchanges does not permit placement of these three post-interchange signs without encroaching on or overlapping the Advance Guide signs necessary for the next interchange, or in rural areas where the interchanging traffic is primarily local, one or more of the post-interchange signs should be omitted."
So: after intersections, unless there isn’t enough space or you just passed one.
For what it’s worth, I was always interested to see Canadian control cities, on US Interstate signs. Drive north of Seattle on I-5, and the signs indicate that the control city is Vancouver, BC. Drive north of Great Falls, MT, on I-15, and the control city is Lethbridge, AB.
Of course, the same works from here, southbound: many signs in Lethbridge indicate the way to Alberta Highway 4, connecting to I-15 (using the proper Interstate marker shield), and Great Falls, MT, as the control city.
You’ve linked to your desktop, which doesn’t work for us…
Does it say anything about km markers? Do they still exist?
When I was young, every mile was marked by a roman mile marker, with 100 mile points marked by 18" diameter posts. The replacement km star pickets were rather less noticeable – do they even bother anymore?
Thanks all. I’ll keep that in mind next time I hit the road. It sure seemed that at least some portion of such signs were right in the middle of nowhere - far from any nearby junction. But perhaps I misremember.
In NSW major roads have an abbreviated mile-post system with a simple sign at 5 kilometre intervals with initial letter to the destination town over the distance, e.g. G 25, for Goulburn.
I’ve seen small distance markers which I think are used more by roadside utility managers than motorists.