For modern buildings...

... door spacing on the loading docks!

Might see old doors bricked in and new ones cut in on older structures, but interior layout and load bearing beams often make that impractical and expensive.

  "how else do you or would

Other than the mechanical need for wider radius curves and turnouts  the main difference between modern railroading and 1950's era is the number of customers and spurs was greatly reduced over a period of time after 1950. So the newer the era modeled  less and less small customers and less variety of loose car traffic would be expected. I saw many industries closed and their track removed in my childhood and younger adult years. The loads were shifted to truck transport so I guess it would also make sense to add more trucking facilities to a modern era layout.  I like the look of modern cars and their interesting graffiti but for now I'm building my layout with 1950's era trackage because I like the more varied smaller industries. If I ever decide to update the era I'll just pull up or pave over some of the tracks to make it look more plausible.....DaveB 

Long Cars

The bigger the radius the better.

Otherwise the considerations would essentially be similar - if you're designing a track or industry to fit X number of cars, make sure you're measuring how big those cars are properly. A spur that fits 3 50' cars might only fit 1 85' car.

Industries might be designed a bit larger for larger cars - like Dave said loading doors/spots for 60' box cars will be very different than 40' cars.

(And you want an industry to look like it's actually big enough to use rail service.)

Door spacing

Some warehouses that have been expanded over the years have 50’ door spacing on the older section of the building and 60’ spacing on the newer section.  If there are only two doors, depending on the door width on the boxcars and on the warehouse it seems to be possible to fudge it so both cars have overlap with the doors.  And sometimes 60’ cars are just spotted at every other door on a 50’ door center building.

Google satellite photos, and various railfan photo sites can yield a wealth of info about this when used together.

50 vs 60

Also there's still a lot of 50' boxcars out there, both older Plate C cars (like the old RailBox cars) and the high cube cars like the paper service cars and modern FBOX cars, so shippers/receivers can specify 50' cars if that's what they're capable of handling.

On the other hand, since a 60' Plate F boxcar has so much more volume capacity than a 50' Plate C boxcar, parking two 60' cars at doors 1&3 instead of 3 50' cars one at each door could be a perfectly efficient use of equipment and real estate.

Anybody going further?

Is anyone going further to do things like change the proportions of the layout?  Or intentionally placing more distance between industries or other scenic features?

70' cars have a larger physical presence.  I was wondering if anyone re-orients tracks or layout features to make sure that the railcars don't dominate the scene and have a better proportion to other layout features

  "70' cars have a larger

It would depend on the layout space available so in many cases switching to N scale might be a possible solution ? ....DaveB

Broader radius curves are not the only concern.

You may also need a broader radius for you vertical curves if there are any hills or valleys in your layout.  As an example, when the modular club I participate with sets up, we often end up with small bumps and dips between modules.  Even though we try to make everything even at set up, often on a set up done on a Friday for Saturday & Sunday operation, we find the need to relevel the layout on Saturday morning, and then by Sunday with people bumping into the layout or just some settling, the dips and bumps reappear.

We spec out Kaddee #5 couplers as our club standard, but from experience members have found that #148 (scale size) couplers will work reliably with 40 foot cars.  50 foot cars need #5 size couplers to stay coupled reliably.  Also "coupler droop" needs to be carefully corrected to keep cars coupled reliably.  

If you are running modern 75-85 foot cars, you are going to need to build your layout to passenger train specs.

That odd new door next to an older door

If you look at some older warehouse that were built for 50' cars,  You will notice that some have a new doors cut in the wall next to the old door.  Take 3 doors spaced originally for three 50's cars.  Now it has 5 doors with the new doors just outside of and next to the older doors.   NO   O   ON  in this pattern  People might wonder why the 2 pairs of outside doors are next to each other etc.  It is to support 60' car spacing,

I was just thinking about this earlier

I was thinking about basically the same question earlier, in my mind I was framing it in terms of "operational density". I don't think you're going to achieve the same operational density with a modern prototype. In fact, I know you won't. There are fewer, larger industries, so even with selective compression, you're likely not to have the same density. I love modern stuff, and I want to model more of it, but seeing layouts that have dense operations makes me want to consider someday moving back to the 1960's or 1970's to have more carload freight, smaller trains and locomotives, etc.

Longer trains

You will have fewer sidings and fewer locations.

For example, if you want to run 20 car trains of 40 ft cars, that's roughly a train 15 ft long.  That makes a siding about 18 ft long.  If you want 1.5 train lengths between sidings and 4 stations on your layout , you are up to a about a 180 ft run.

If you want to run 20 car trains of 70 ft cars, that's roughly a train about 18 ft long, making a siding about 21 ft long.  If you want 1.5 train lengths between sidings and 4 stations you are up to about 210 ft of run.  If you only have a space to accommodate 180 ft, you are now faced with reducing the siding spacing or the number of stations.

That was actually one of the reasons I went to the 1900 era.  I can put a 15 car train in 8 ft siding, 

Time

One other thing is that it will take longer to switch, because the shoves are longer because the cars are longer, assuming you are dealing with the same number of cars.

Its amazing how that can really affect things.  A friend of mine put #8 switches on a  yard switch lead (once).  It looked cool, but was extremely tedious to switch because it felt like it took forever to saw back and forth from one track to the other while switching.  It materially affected the capacity of the yard to switch.

Longer cars will have a bit of the same issue. 

  "if you want to run 20 car

I think the difference is more than that?  70 foot cars are 30 feet longer than 40 foot cars so 20 times 30= 600 feet divided by 87=almost 7 feet in HO scale. or a siding of about 25 feet? .....DaveB

How long is a car?

A 40 ft car is really about 45 ft long, so how long is a 70 ft car?  Is that 70 ft inside length, is it 70 ft over couplers?

I assumed that a 40 ft car was inside length and that a 70 ft car was over the couplers (60-65 ft IL).

I also added one extra car to a train for the 40 ft car lengths to allow for a caboose, but didn't include an extra car for the 70 ft car trains. 

Either way, the point was the same car count train will be longer and therefore a modeler will have fewer stations/sidings or closer stations. 

I have had this discussion about "big trains" with several people designing their layouts.  They want really long trains, 20-25 ft long, and then put sidings about 25 ft apart.   Its hard to convince them that that what they did was take a really big layout and make it into the same siding spacing/train length ratio as a 4x8 layout.  Running a 15 ft train and having sidings 30 ft apart will seem bigger than a 25 ft train with sidings 25 ft apart.

Since car count determines switching activity, the number of cars affects the amount of thinking the switchers and locals have to do.  If I lengthen the cars and reduce the car count because space is constrained, then I reduce switching opportunities.  Another consideration is that as I go more modern in eras the amount of "detail" switching is reduced, the number of "work events" are reduced.  Yes, there are still places that do detail switching, but they are fewer and farther between. 

Other things are also in there.  In the 40 ft car world there it's more likely to have an engine facility and engines would be serviced more frequently (smaller fuel tanks).  Engines would be changed out more frequently.  In the 70 ft car world, more engines would just be tied up on a track and serviced less frequently (bigger fuel tanks).  Engines would be changed out less frequently.  A unit train from Wyoming to Georgia could make a half dozen or more round trips on the same train, 18,000 miles without changing engines or the cars materially.  In the 40 ft car era a solid coal train would change engines and cars every 200-500 miles.

Longer equipment

If you want to model the modern era, you can’t use 40’ cars, you need to go with modern cars.

Adequate curve radius and easements are key for longer cars - a good easement will let you use a slightly tighter radius without excessive coupler misalignment entering and leaving curves.

Higher number switches do take more time to traverse, but they look more realistic with longer cars, and if you adjust your mindset from how fast you can bang cars around to enjoying the movement of the equipment while you operate it’s nice.  I had #10 turnouts on my N scale switching layout and I liked the way they worked out - I’d do it again in N and if I had the space I’d use #10 in HO.  Why #10?  I measured frog number of an accessible turnout on the prototype I was using as inspiration for the layout, and it was #10.

Modern era industries do tend to be bigger and have more cars spots for longer cars.  But if you look around a bit there are still examples of smaller industries that use the same longer cars, but only a few of them.

Some HO scale car length notes I’ve been referring to while planning my switching layout: