"Most subdivision regulations list the minimum required width of pavement for all of the types of roads allowed in the municipality. In
general, a “travel lane” is 9 – 10 feet, so the most narrow requirements are 18 – 20 feet of pavement. The average car or pickup is 5.5
– 6.5 feet wide, and dump trucks and school buses are 7 feet. The rationale for roads wider than 20 feet is the need to accommodate
parked cars and two-way traffic, as well as emergency vehicles."
So if we assume a 20 foot wide road, it will translate into 2.759 inches in HO scale(1/87).
Mac, the typical standard for a Texas Farm to Market road is 16 feet although paved roads can go up to about 20 feet. A 20 foot wide road would be about 2.6" and a 16 foot wide road would be about 2.20". Most of the FTM roads have easements of about 5' from each road edge although this varies depending on how close the farmer's property line is to the road. The easements are usually just grass and weeds, sometimes mowed. Except for a few inches of gravel extending beyond the road edge for paved roades, there are amlost never any shoulders.
Some good answers, but I have to chime in on this one...
It depends on your era more than anything else, but you will not find many FM roads in Texas with a right-of-way narrower than 50 feet, equal to roughly 6.9 inches in HO scale. The right-of-way is that swath of land from fence to fence including the paving, ditches, signs, utilities, etc. I assume when you ask about "easement" the right-of-way is really what you're talking about (it's more of a legal distinction than anything else).
In the modern era, TxDOT requires a 4 foot [0.55 in.] shoulder outside the driving lane. Many times it's weed covered and is often just base course asphalt, so it can appear to be narrower. Years ago the 4 foot shoulder wasn't required, but the base course asphalt always extends past the driving lane, so there's at least some paved shoulder. Not only that, the roadbed is graded wider than the paving section to avoid having the roadway edges deteriorate over time.
You may have lanes as narrow as 10 feet [1.38 in.], but recommended practice is 12 foot [1.65 in.] lanes. Yellow striping in between opposing lanes of traffic is one foot [0.14 in.] wide (space dedicated for a four inch [0.05 in.] yellow stripe, a four inch space and a four inch yellow stripe regardless of the striping pattern), and the outer white stripe is four inches wide, so really your lanes are only 11 feet 4 inches [1.56 in.] wide when you use a 12 foot section. With a 10 foot lane, the drivable area between stripes is only 9 feet 4 inches[1.29 in.], and since modern highway trailers are 102 inches wide (8 feet 6 inches) [1.17 in.], there's not much room for error, hence the recommended 12 foot width.
Things get tricky for the dimensions of passing lanes, turn lanes, etc. which are based on design speed, grade, visibility and other criteria. I usually let TxDOT give me the dimensions after I take a stab at it. I guess it's a case of me throwing them a bone on what I think the dimensions should be and they come to the rescue with the correct answer.
Again, another assumption, but since you live in Keller and I do projects for TxDOT in DFW and Houston, I'm going by the Texas standards, which may or may not be what you need. But, in any case, I must recommend the Texas Manual on Uniform Traffic Control Devices because it's a well illustrated and clear handbook for how things should be designed and the space required for various situations. And the fact you don't have to be an engineer to understand it helps, too. Check it out:
I'm modeling 1990's through today. My grain facility is a condensed version of the Cassidy Grain facilities in Snyder, OK. Technically I'd need the ODOT numbers but I'm more then willing to go with TXDOT stuff. I just don't count that many rivets. I can't imagine that there would be too many differences anyways.
Rotor, that's why I said about. I always compress secondary roads like that since the difference is hardly noticeable and it gives a few more fractions of an inch to work with somewhere else.
RTH, that's some good information. I was thinking more of shoulders than legal easement but you're right, I think that the state took 50' easements from farm owners as a condtion of building the FTM roads. Some of the FTM dirt and gravel roads couldn't have been more than sixteen feet wide though. I could not pass a grain truck with my motorhome unless both of us got off on the side. I'll go with the paved roads being 20 or 22 feet but some of those older roads are pretty narrow. Don't even get me started on Texas's weird on and off ramp arrangements on freeways.
Man, wouldn't you know it, but I haven't touched a TxDOT project since March when we got construction approval for our plans. Today that project came up at work since it's going to construction. Coincidence? Or just plain jinx?
I wouldn't be surprised to find out that there are some roads that narrow, especially in days gone by. And I agree with the idea of "selective compression" as a good approach for most people, though I choose to model much smaller areas and do them as close to scale as possible. Just personal preference.
I did a google on roadway widths years ago, and found a couple of sites that had info on this subject. But, those sites seem to have disappeared, but fortunately, I had saved the files somewhere.
It was interesting because one was a County document, and the other was a township document. The latter told you the dimensions for a lot of different applications, like 25mph residential streets, to main streets with angled parking. I might have posted that file here, it's in the archives under my handle.
On the more practical side, I wanted to put in a road I was familiar with on my layout. But, since that road was in Indiana, I had a friend of mine who's from there go out an measure it for me! Once I got that, I did the math thing to size down to HO.....
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