theholtsite

So apparently a plane landed on a stretch of highway around 5 miles from our house. It was all over the news today (article here).

I had heard somewhere that the original Interstate Highway System (established by Eisenhower) required that one mile in five be straight and level for emergency plane landings. So I did some research (well, I read this wikipedia article). Here’s some interesting facts about the highways that we take for granted every day:

1) Initial federal planning for a nationwide highway system began in 1921. The initial cost estimate for the system was $25 billion over twelve years; it ended up costing $114 billion and taking 35 years to complete.

2) Interstate Highways often have the highest speed limits in a given area. Speed limits are determined by individual states. Rural limits generally range from 65 to 80 mph, and urban interstate speed limits are generally 50 to 65 mph across the country.

3) Contrary to popular lore, Interstate highways are not designed to serve as airstrips (oh well… at least it worked yesterday!)

4) In addition to being designed to support automobile and heavy truck traffic, interstate highways are also designed for use in military and civil defense operations within the United States, particularly troop movements.

5) An option for maximizing traffic throughput on a highway is to reverse the flow of traffic on one side of a divider so that all lanes become outbound lanes. This procedure, known as contraflow, was first employed in the 1998 evacuation of New Orleans, Louisiana in preparation for Hurricane Georges.

6) Primary Interstates are given one- or two-digit route numbers. Most Interstates have two digits; there are only three one-digit Interstates in the system: I-4, I-5 and I-8. East-west highways are assigned even numbers, and north-south highways are assigned odd numbers. Odd route numbers increase from west to east, and even numbered routes increase from south to north, though there are exceptions to both principles in several locations. Numbers divisible by 5 are intended to be major among the primary routes, carrying traffic long distances.

7) About 56% of the construction and maintenance costs are funded through user fees, primarily gasoline taxes, collected by states and the federal government, and tolls collected on toll roads and bridges. The rest of the costs are borne by the federal budget.

8 ) By threatening to withhold highway funds, the federal government has been able to stimulate state legislatures to pass a variety of laws.

9) The longest Interstate highway is Interstate 90, which runs 3099 miles between Boston, Massachusetts and Seattle, Washington.