If you could go back in time once and influence a single decision...

[jeffandnicole]

Not sure if this counts as a “single decision”, but I’d go back to 1939 and make the Pennsylvania Turnpike’s design specs more modern, setting a wider minimum median width, wider minimum ROW width, and higher-speed interchange geometry.
Since the Turnpike served as the archetype for Pennsylvania’s limited access highways built in the ensuing two decades, it’s possible that a broader and more modern Turnpike would have saved the older portions of I-70, I-83, the Schuylkill, etc. from being so unfortunately under built.
At the very least, had the ROWs and medians been wider, we’d have more space for modernization and capacity expansion.

I would revise that decision to setting more modern standards on the -extensions- of the Turnpike starting in 1950. 

I will grant that the original 160 miles that was opened in 1940 had ok standards for the day, and nobody really knew how successful it would be trafficwise.

That way the extensions could have served as the model for other superhighways in the state.

You do understand that modern standards aren't the same thing as futuristic standards, right? 

If we were to build something today, we're using modern standards in 2017.  We're not using what modern standards will be in 2077.

[Beltway]

Not sure if this counts as a "single decision" , but I'd go back to 1939 and make the Pennsylvania Turnpike's design specs more modern, setting a wider minimum median width, wider minimum ROW width, and higher-speed interchange geometry.
Since the Turnpike served as the archetype for Pennsylvania's , it's possible that a broader and more modern Turnpike would have saved the older portions of I-70, I-83, the Schuylkill, etc. from being so unfortunately under built.limited access highways built in the ensuing two decades
At the very least, had the ROWs and medians been wider, we'd have more space for modernization and capacity expansion.

I would revise that decision to setting more modern standards on the -extensions- of the Turnpike starting in 1950. 
I will grant that the original 160 miles that was opened in 1940 had ok standards for the day, and nobody really knew how successful it would be trafficwise.
That way the extensions could have served as the model for other superhighways in the state.

You do understand that modern standards aren't the same thing as futuristic standards, right? 
If we were to build something today, we're using modern standards in 2017.  We're not using what modern standards will be in 2077.

I was responding to the idea of the 1939 Turnpike standards being inadequate and directly influencing the next two decades of PA limited access highway construction.

I merely revised that to the 1948-1950 standards of the Turnpike extensions.  They did not update the 1939 standards and used them on the rest of the east-west turnpike and NE Extension.

His statement about the 1939 Turnpike standards is correct, but the problem is that they used the same standards on segments built from 1948 to 1957.

Turnpikes built in other states in the 1950s used much wider medians and clear roadsides, specifically in NY, MA, NJ, OH and IN.  No reason why the PA Turnpike extensions in the 1950s couldn't have done likewise.

[Beltway]

Also Virginia could've considered a limited access highway instead of just an arterial along US 58 from Hampton Roads to I-85 (I hear people saying to I-95 but that's not good enough in my eyes as I-85 is the more important route south of Virginia because it connects to a larger population). Even in it's 4 laned configuration, US 58 is hazardous along this entire stretch because of increasing long distance traffic on a road with many at-grades and private entrances, leading to numerous accidents including many fatal ones over the years.

Getting it funded in the 1960s or 1970s would have meant that it would need to be in the 1956 or 1968 Interstate system, it would have difficult or impossible to fund without the 90% FHWA funding for Interstate highways, as the other FHWA funding categories were not more than 50%.

While it looks like an Interstate omission from today's standpoint, given that there is no southerly Interstate connection between Hampton Roads and I-95 and I-85 (no logical driver would use I-64 to do this), there are reasons why IMHO that it was not authorized in the 1956 or 1968 Interstate system.

1) An Interstate highway was allocated to serve the entire Hampton Roads area in 1956, that being I-64.
2) I-664 was allocated in 1968 to provide a second crossing of the Hampton Roads estuary.
3) The state of Hampton Roads crossings and Elizabeth River crossings even in 1968 was limited in capacity to where it considerably limited travel in the region.
4) Virginia Beach wasn't incorporated to its current size until 1965.
5) Traffic volumes on US-58 in Southside Virginia in the rural areas were low even in 1968.
6) US-58 between Martinsville and I-64 in Hampton Roads was authorized for upgrade to 4 lanes divided with town and city bypasses in 1964.

In 1956 when the national Interstate highway System was begun, Norfolk was a somewhat sleepy Navy town.  The only fixed link across Hampton Roads was the two-lane, out-of-the-way US-17 James River Bridge that was built in 1928, and it was narrow, with a roadway deck 22 feet wide between parapets.  There were vehicular ferries between Norfolk and Hampton.  Hampton Roads was a major transportation barrier that effectively divided the area into two separate metropolitan areas, with little interaction.  The 3.5-mile-long Hampton Roads Bridge-Tunnel (HRBT) was two lanes wide and it opened in 1957.  It wasn't until 1976 when the parallel HRBT span was built, completing Interstate 64 in the Hampton Roads area, that major highway capacity existed to truly unify the Peninsula and South Hampton Roads areas into one metropolitan area.

The US-17 James River Bridge was replaced with a modern four-lane bridge in 1982, providing more capacity.  The four-lane I-664 bridge-tunnel was completed in 1992, completing the beltway around the area.  Today 12 lanes on three separate facilities provide excellent linkage across Hampton Roads, that also generates more traffic in and out of the whole region.

US-58 between I-95 and I-64 is all 4 lanes and has considerable amounts of higher-type design, 39% of the length is freeway standard and another 11% is expressway standard.  That does provide speed and safety advantages on those segments.  Certainly the potential is there to build freeway segments to eventually provide a freeway for the whole length, that is what I would advocate.

[sparker]

Back in 1973, when the concept of adding new Interstates was, by that years' Federal legislation, devolved to the states with no federal chargeability aspect available, I would have pressed for modification of that to essentially allow a periodic (every 10 years would suffice) new group of Interstate highways, with an aggregate mileage limit of, for example, 2500 miles, to be commissioned with a slightly reduced (83.33 or 85%) federal input (conceptually similar to the 1968 additions but with the reduced federal dollar input).  The states would still be allowed to petition for Interstate mileage on their own in the interim years -- but any such routes would be subtracted from the amount allowed on the ensuing 10-year plan; Howard-Cramer or "transferred" mileage being the exception. 

With such a concept in place, Interstate additions would, for the most part, remain a nationally-considered concern rather than the product of local machination that characterizes many of today's proposals.  It would allow for the addressing of demographic shifts as delineated in census data on a regular basis rather than haphazardly and, often, politically influenced.  As with the original Interstate plan as well as the '68 additions, there, of course, would be some measure of politically-motivated input -- but at least it would be more out in the open than the methodology currently utilized in the arena. 

But '73 was the time of the Nixonian "block grant" legislation truncating federal programs and shifting things to state & local jurisdictions; a renewed national concept such as this probably would have been stopped in its tracks.       

[JasonOfORoads]

Build the West Side Bypass around Portland when it was brought up 40+ years ago.

Also, force Vancouver, WA to be served by MAX light rail when the Yellow Line was built.

[sparker]

Build the West Side Bypass around Portland when it was brought up 40+ years ago.

Also, force Vancouver, WA to be served by MAX light rail when the Yellow Line was built.

I was attending PSU when the original LR extension across the river was being debated back in 1994; since the state line goes down the river -- and Vancouver, as a result, is not a part of Portland Metro -- there was no leverage to be had regarding "forcing" Vancouver or any other WA city to defer to any such extension.  It was voted down about 40-60%; the two arguments carrying the day were that (1) WA sovereignty was being attacked by OR-based institutions, and (2) Vancouver & environs had no intention of functioning anything like Portland -- and that the LR extension was the "nose through the door" regarding an inter-state expansion of regional government.  Essentially "tribal" arguments; it was suggested at several Vancouver/Battle Ground town meetings (I sat in on a couple of these) that Portland-based criminal elements (gangs) would use the LR to expand their territory and start selling drugs north of the river!  A spurious argument -- but one that had more than a little traction. 

This region of southern WA relishes the fact that it isn't Portland; the area has seen quite a bit of housing and commercial development that would likely not have passed Metro muster south of the river.  Of course, the residents there blithely and regularly venture across the bridges to take advantage of the lack of sales tax in OR!

[froggie]

^ That may come to bite them in the arse someday, especially when/if the Interstate Bridge fails.  Portland can survive without Vancouver far more than Vancover can survive without Portland...