Awkward looking bypasses (adds additional mileage)

[SkyPesos]

I just assume an even number is just a normal bypass 

Way too many exceptions to that.

[HighwayStar]

I just assume an even number is just a normal bypass 

An even number should be a loop, ie. it returns to the parent route, but unfortunately that rule is not well implemented.

And even some loops which have even numbers are not the bypass but the main route.

[sprjus4]

How about even numbers that connect one interstate highway to another?

[oscar]

The Asheboro bypass is useless.

Huh? Like many other good bypasses, it lets through travelers avoid a slow slog, and multiple traffic lights, through town. It also speeds up local travel, by reducing through traffic on what is now the US 64 business route.

I've been there, to clinch the bypass soon after it opened, and also part of the business route to shop at the local Wal-Mart.

[HighwayStar]

How about even numbers that connect one interstate highway to another?

There are plenty of examples of such numbering, but it would be better to strictly apply the loop rule as returning to the parent, as motorists can then be sure that if they take the bypass they can return to the route they were on, whereas going to another highway is not especially useful information and might be better designated as a spur if that is all it does.