Difference between US Highways and Interstates

[DevalDragon]

I know this seems like a stupid question - but what is the difference / reasoning for designating  US Highways vs. Interstates? I'm talking about the US highways built to Interstate highways that connect to them like US 75 from Dallas to Oklahoma or US 190 from Belton to Copperas Cove (TX) orUS 131 in Michigan. They are built to Interstate Standards but they are still designated as US Highways.

Why? Is this a funding issue or something like this?

[amroad17]

A state DOT wanting a freeway to become an interstate highway has to submit an application to AASHTO, the American Association of State Highway and Transportation Officials.  This involves reasons why and number desired--unless it is written into law, such as I-99, I-73/74 in the Carolinas, and I-86 (eastern).  AASHTO then makes a decision whether to accept or reject/deny with reasons stated for the rejection.

Your examples of US 75 and US 131 would be rejected by AASHTO because they are freeways that do not lead to major points where they currently end.  If US 75 was an interstate standard freeway from Dallas to Tulsa (or even as far as I-40 in OK), then Texas and Oklahoma DOT's would have to submit an application to AASHTO requesting that the US 75 freeway become Interstate 45, for example.

Some state DOT's may not want to bother with the application of changing a freeway into an interstate highway because the current freeway has had a certain number for many years.  Saying this, these state DOT's had to apply to AASHTO to move US highways onto these freeways that were built (US 131, US 23 in MI; US 35 in OH; US 20 in IA).

So you see, it is up to the state DOT's to desire changes in numbering from US to Interstate as long as they submit an application to AASHTO.

[hbelkins]

FHWA has more of a role than AASHTO, and FHWA has the final say.

Wonder if any states have ever bypassed AASHTO and gone straight to FHWA for an Interstate designation?

[1995hoo]

Interstate designation was arguably more important in the late 1980s/early 1980s after Congress amended the NMSL to allow the 65-mph speed limit on rural Interstates only. There are a number of examples of routes that were redesignated as Interstates during that period to allow for the posting of 65-mph limits. Since the states regained their rightful control of speed limits in 1995, it's arguably a lot less of an issue.

The situation "amroad17" mentions about a number that's been in place for many years is the reason Maryland cited for never posting the approved I-595 designation for part of US Route 50.

[huskeroadgeek]

Interstate designation was arguably more important in the late 1980s/early 1980s after Congress amended the NMSL to allow the 65-mph speed limit on rural Interstates only. There are a number of examples of routes that were redesignated as Interstates during that period to allow for the posting of 65-mph limits. Since the states regained their rightful control of speed limits in 1995, it's arguably a lot less of an issue.

The situation "amroad17" mentions about a number that's been in place for many years is the reason Maryland cited for never posting the approved I-595 designation for part of US Route 50.

Before they returned to allowing states to set their own speed limits, they also amended the 65 mph law for rural interstates to allow for non-interstates built to interstate standards to carry the 65 mph limit. As an example, I know the US 67 freeway in Arkansas was allowed to carry a 65 mph limit.

[1995hoo]

Right, but prior to that amendment Interstate status mattered more. Funny, nowadays the road with the highest speed limit is a non-Interstate (the 85-mph segment of Texas 130).

[Mr_Northside]

They are built to Interstate Standards but they are still designated as US Highways.

In some instances, whatever jurisdiction decided that some corridor needed the safety / capacity improvements that a freeway meeting interstate standards provides, but didn't care about or want an Interstate designation, mostly for reasons outlined in posts above. 
Often the roadway standards are determined by those needs by engineers.  Decisions about whether it should be in interstate, especially in the last couple of decades, are often made by politicians touting economic stimulation (rightly or wrongly in any given situation.)

There's a smorgasbord of threads on the forums debating the merits of various interstate route designations/highways.

[Duke87]

A lot of it today is politics. The original federal interstate funding is gone, and the feds have been a-ok with providing funding for projects not on interstates. As such, there is no longer any fiscal benefit to making a freeway an interstate, and all you are left with is the strings attached (interstate design standards, needing federal approval to change the designation, etc.). For this reason many states have pretty much decided not to expand the interstate system within their borders.

So why, then, are we still getting new interstates? Well, for one thing, the feds still do meddle in the affairs of freeway construction and in some cases (I-69, I-99) have legislatively mandated an interstate designation for a freeway that's being built.
For another, some jurisdictions like the idea of introducing an interstate to serve an area not currently on the interstate system (even if the freeway already exists - see US/I-41 in Wisconsin) because they perceive it will boost the local economy and bring more prestige to the area (hey, they've got an interstate now!). From a design perspective the designation on a road is irrelevant to how useful it is, but humans are emotional in their perception of things and an interstate shield makes a highway seem better even if it isn't.

[DevalDragon]

Is there any benefit to changing the designation from US Highway to Interstate Highway, besides nice new shields and new maps?

[vdeane]

Depends on whether you consider the interstate shield just a brand name or whether you think of the addition as becoming part of an American comprehensive road system rivaling the autobahn.

[PHLBOS]

Depends on whether you consider the interstate shield just a brand name or whether you think of the addition as becoming part of an American comprehensive road system rivaling the autobahn.

When the Interstate Highway System was initially conceived, the Autobahn was indeed used as a guide/reference.

[vdeane]

Given Eisenhower's experience, I'd say it was the inspiration.

[roadman65]

Someone mentioned that some states applied for interstate status to get the 65 mph speed limit as it was only granted to interstates back before 1995.  However, I once read that any freeway that is built to interstate standards that connected to the interstate system, did qualify.

Even DelDOT, before 1995 was planning to allow the DE 1 Turnpike to be signed at 65 mph if the national speed limit was never given back to the states.  They would have not signed the Smyrna- Dover Bypass as such until the mid section was completed, but nonetheless in the day all of DE 1 that is freeway could be signed under old ruling.

That brings up the fact, that Kansas (or specifically KTA) did not need the I-335 designation considering that from Emporia to Topeka where originally the Kansas Turnpike was unnumbered was connected at both ends to interstate designations.  Also, the Kentucky Parkway System was at 65 mph because they all connect to that state's interstate system.

[NE2]

Someone mentioned that some states applied for interstate status to get the 65 mph speed limit as it was only granted to interstates back before 1995.  However, I once read that any freeway that is built to interstate standards that connected to the interstate system, did qualify.

Only if the state applied: http://www.nytimes.com/1987/12/29/us/20-states-to-win-the-right-to-set-a-65-mph-speed.html

[hbelkins]

It took legislation sponsored by Mitch McConnell to get the 65 mph limit applied to non-Interstate freeways. Kentuckians weren't happy because they could drive 65 on the interstates, but had to slow down to 55 on the parkways.

[roadman65]

Interesting that DelDOT did not give me ALL the facts back then.

Anyway on another note, I was reading in the website for the current Alexander Hamilton Bridge renovation project in NYC, and of course being that the bridge carries I-95 across its span it qualifies for federal funding (in which I am sure Bloomberg is quite pleased of) in which the City of New York only has to flip for 10 percent of the cost of rebulding with the rest from Washington.  US routes are essentially state routes like any other state routes within one state, only really part of a larger network on paper with the FHWA and therefore do not get extra help or at least as much as 90 percent like the interstates do.

[PHLBOS]

If memory serves, and I read this during the early 1980s on a Rand McNally road map for the Eastern United States; while the Interstate is indeed a federal system (funding distribution and all); the US highway system is not a federal system.  That's one difference right there.

[roadfro]

Be careful about using the term "federal"...especially don't refer to either type of highway as "federal routes"...

I think the key differences are in the design standards, the "system" and the funding formulas.

An Interstate is always (with small exception) a freeway-grade facility, making the Interstate system a national network of interconnected freeways. Generally speaking, new construction and major reconstruction efforts on the Interstate system have come from a 90/10 funding formula, where 90% of the funding is supplied from federal funds and state/local pays the remaining 10%.

A US route can vary between two-lane highway, city street, or freeway designed to Interstate standards--any newly designated US route is supposed to conform to AASHTO's latest design standards (which is a component on the route application). The US routes are therefore a network of interconnected highways that (theoretically) are up to a minimum standard for national travel.

Funding for US routes can vary.* They are not automatically part of an overall system of importance (like the Interstates are virtually automatically incorporated into the National Highway System). US routes can act more like state highways in this regard...if it's classified as part of the NHS or some other ranking system, construction funding can be like an 80/20 match--if the route is a lower functional class or other system, the funding shifts significantly more to the state.
[* Note I am not an expert on highway funding, so forgive if these details are less than accurate.]

[roadman65]

Be careful about using the term "federal"...especially don't refer to either type of highway as "federal routes"...

I think the key differences are in the design standards, the "system" and the funding formulas.

An Interstate is always (with small exception) a freeway-grade facility, making the Interstate system a national network of interconnected freeways. Generally speaking, new construction and major reconstruction efforts on the Interstate system have come from a 90/10 funding formula, where 90% of the funding is supplied from federal funds and state/local pays the remaining 10%.

A US route can vary between two-lane highway, city street, or freeway designed to Interstate standards--any newly designated US route is supposed to conform to AASHTO's latest design standards (which is a component on the route application). The US routes are therefore a network of interconnected highways that (theoretically) are up to a minimum standard for national travel.

Funding for US routes can vary.* They are not automatically part of an overall system of importance (like the Interstates are virtually automatically incorporated into the National Highway System). US routes can act more like state highways in this regard...if it's classified as part of the NHS or some other ranking system, construction funding can be like an 80/20 match--if the route is a lower functional class or other system, the funding shifts significantly more to the state.
[* Note I am not an expert on highway funding, so forgive if these details are less than accurate.]

You actually phrased what I was trying to say perfectly.