Another thread had me thinking about this. US 59 from Cleveland to Livingston (and Lufkin has it too) has not had the I-69 fairy tap it on the forehead yet, so there are some exits in Cleveland, Shepherd and Livingston with exit numbers. I was driving this stretch this weekend and noticed something weird. The numbering ascends southbound which tells me it's Texas reference marker based, but the odd thing is, all the exits have letter suffixes. In Shepherd, the first exit heading northbound is 453B, then the second is 451B. Why are they letter suffixed? Even more perplexing is they have different letter suffixes in the southbound direction. Southbound the exits are 451C and 453A. Why does Texas have to do things so weird? Makes me think of US-75 coming out of Dallas, for some reason has exit numbers, and they are sequential, and so does US 54 in El Paso and they start at 22 for some reason. Why does this crap happen? At least I-17 has an interesting story as to why it starts at mile 194. Why does Texas have to use the stupid reference marker system and why don't they just go to mile markers like smart people?
I've long suspected the Texas reference marker system has upward progression from north to south because this keeps the origin point in US territory. If it went from south to north (the way milepointing works nearly everywhere else), the origin point would likely be somewhere in Mexico.
As for the exit numbers having suffixes, I wonder if this is a revival of the old system (I think used on one or several of the very early freeways in Texas) of giving each ramp its own exit number.
Quote from: J N Winkler on August 31, 2020, 10:49:28 PM
I've long suspected the Texas reference marker system has upward progression from north to south because this keeps the origin point in US territory. If it went from south to north (the way milepointing works nearly everywhere else), the origin point would likely be somewhere in Mexico.
As for the exit numbers having suffixes, I wonder if this is a revival of the old system (I think used on one or several of the very early freeways in Texas) of giving each ramp its own exit number.
Until about the early nineties All of the interstates in Texas had sequential exit numbers. That said, no the mess on US 59 is a result of the use of randomly assigned reference markers. Reference markers are GPS markers along the roadway. An engineer or technician checks out a string of them and assigns them (generally sequentially)> There is not any continuity between TXDOT districts unless it is coordinated at the time the first district does theirs.
The positive thing and something EVERYONE knows is these exit numbers are just temporary. In around 5 years the ones on this stretch will be gone.