Road Trip Trivia II: Interstate Trivia

November 27, 2013

Last week, we offered odd highlights of automotive history to help you through the Thanksgiving traffic jams. With the holiday season in full swing, we figured you may need more to last you through the next big family gathering. Here’s some quality trivia (and a few pernicious myths) about the Interstate Highway System.

Interstate Trivia: Longest, Shortest, Oldest, and Most Expensive Routes

Someone in the car – where you keep your captive audience during road trips – always wants to know about the extreme outliers in any topic. Here’s a convenient breakdown of extremes within the Interstate Highway System:

Credit: Todd Lappin

  • The Shortest Route is I-97, at 17.5 miles. Beginning and ending in Maryland, I-97 connects Annapolis and Baltimore.
  • The Longest Route is I-90, running 3,085 miles from Seattle to Boston.
  • The Longest North-South Route is I-95 (Florida to Maine, 1,892 miles), which was also
  • The Most Expensive Route to construct, with a final cost of $8 billion.
  • I-95 claims a third entry for passing through the most states, at sixteen.
  • Texas contains the greatest Interstate mileage per state within its borders, at 3,233 miles.
  • The oldest section of the Interstate System actually pre-dates it. The Grand Central Parkway in Queens, NY was constructed in 1936 and eventually designated I-278 within the system.

That should keep the min-max contingent occupied, while you tuck into the meatier subject of Cold War mythology.

Interstate Myth: One mile in every five is an emergency airstrip

Public DomainDon’t feel bad, I fell for this one. According to the myth, Cold War contingency planners demanded integration of emergency air strips in every fifth mile of the Interstate Highway System. While it’s true that a national air strip system convenient (and roughly parallel) to Interstate routes was proposed in 1944, no language mandating them was written into the spec.

Richard F. Weingroff, the Federal Highway Administration’s “unofficial historian” and information liaison specialist for the Office of Infrastructure, wrote an admirably constrained take down of the one-in-five myth for the May/June 2000 issue of Public Roads:

I don’t know if 10 percent of the Russian government’s income comes from the sale of vodka. I don’t know if a cow can go upstairs, but not downstairs. And I certainly don’t know if a duck’s quack doesn’t echo.

But I do know the following statement is false: The Eisenhower Interstate Highway System requires that one mile in every five must be straight. These straight sections are usable as airstrips in times of war or other emergencies.

Public DomainWeingroff traces the origin of this myth to a flight strip program jointly operated by the Public Roads Administration (now the Federal Highway Administration) and the Army Air Force. Congress considered adding funds for its expansion along the Interstate system to the 1944 Federal Aid Highway Act, but never did. The one-in-five myth sounds entirely plausible – given its Cold War origins – but nothing like it was any part of any version of the Interstate Highway plan.

Interstate Myth: I-76 was assigned its number to honor the events of 1776

Credit: Wikimedia CommonsThis myth is an odd combination. While plausibility lends it resilience, it’s also a spectacularly uninteresting bit of trivia and a complete failure as a conversation starter.

I-76 was named in accordance with the standard numbering system laid out in the Federal Aid Highway Act of 1956. In outline:

  • Even numbers go east-west, odd numbers north-south.
  • Numbering starts in the south for east-west routes and in the west for north-south.
  • Regular Interstate routes are assigned a two-digit number, while beltways, bypasses, and spurs use three-digit designations.
  • For three-digit designations, spurs (connected to the Interstate on one end) begin with odd numbers, while beltways and bypasses (beginning and ending on the Interstate) start with even numbers.
  • The final two numbers for a spur, beltway, or bypass indicate which Interstate route it serves; ie, I-587 in New York is short spur off of I-87.
  • While the main routes follow a national naming system – so there’s only one I-95 – spurs, bypasses, and beltways are numbered within each state.

So, no. I-76 was just the next available number and was not selected for historical significance. It does veer south towards Philadelphia at Valley Forge, though, so consider making a stop on your way from Ohio to New Jersey.

Public Domain

Interstate Trivia: Why 55?

There is no Federally-mandated speed limit on the Interstate Highway system, yet many Routes and highways hover around the 55 mph mark. Have you ever wondered why that is? There are no solid engineering or performance-related reasons, just more fallout from the Yom Kippur War and oil embargo of 1973.

Credit: David LofinkBefore 1973 – and since 1995 – states were allowed to set their own speed limits on Interstate Highway Routes within their borders. As conservation measure during the oil crisis, Richard Nixon proposed a 50mph limit on passenger vehicles, to compliment restricting gas sales on Sundays and tweaked refinery output. Congress settled on 55 mph as part of the Emergency Highway Energy Conservation Act of 1974, which capped speeds on all roads at 55 mph and mandated 55 mph on Interstates. Non-compliant states were to receive no federal funds for highway repair.

Fuel savings from the program fell far short of the estimated 2-3%, with sources pegging actual reductions from .5% to 1%. This was partly due to driver resistance and defiance from state governments, who – in some cases, and unofficially – directed law enforcement to ignore the new limits. The limit was raised to 65 mph in 1987 and done away with entirely in 1995.

Do you know any other interesting facts about our nation’s highway system? Tell us below.