Interstate Standards

[CtrlAltDel]

I have long had an interest in how the various standards for the Interstates were determined and how they've changed over time. To that end, I've been trying to collect the various standards publications. I have 2005 and 2016, but I have not been able to get hold of a copy of the earlier ones, including what I think is the first one from 1956.

If you have any ideas on how I might be able to procure these, or if you have a copy you are willing to share, or even just random comments on the standards, I'd appreciate your help.

[kevinb1994]

I have long had an interest in how the various standards for the Interstates were determined and how they've changed over time. To that end, I've been trying to collect the various standards publications. I have 2005 and 2016, but I have not been able to get hold of a copy of the earlier ones, including what I think is the first one from 1956.

If you have any ideas on how I might be able to procure these, or if you have a copy you are willing to share, or even just random comments on the standards, I'd appreciate your help.

Hope this aids in what you're looking for: https://www.fhwa.dot.gov/programadmin/standards.cfm

[Mapmikey]

Here is a fully viewable version of the 1956 standards - https://babel.hathitrust.org/cgi/pt?id=mdp.39015021030310;view=1up;seq=1

The next version was from 1963...full view here:  https://babel.hathitrust.org/cgi/pt?id=uc1.c101179750;view=1up;seq=2

Other versions are search only/limited view from this website (1965, 1991)...

[J N Winkler]

In terms of primary-source documents, the first set of Interstate standards actually appeared in 1944, as part of the Interregional Highways report.

https://babel.hathitrust.org/cgi/pt?id=wu.89090507336;view=1up;seq=5

[froggie]

Of note regarding Interstate standards, the 1967 Highway Act mandated two things:  that shoulder widths be carried across bridges longer than 200ft, and that Interstate segments be built with 4 lanes regardless of low traffic forecasts.

[DJStephens]

The Gila River / Wash Bridge that carries I-10 east of Phoenix might be one of the longest remaining "narrow" examples.   Virtually no deicing chemicals, in the area, has surely lengthened it's lifespan.   

[Max Rockatansky]

The Gila River / Wash Bridge that carries I-10 east of Phoenix might be one of the longest remaining "narrow" examples.   Virtually no deicing chemicals, in the area, has surely lengthened it's lifespan.

Really you could say the same about much of the bridgework in the state in general.  There are so many examples of early 20th bridges in Arizona in relatively good repair whether they are on active roadways or not. 

[CtrlAltDel]

Thank you very much for these links. I'm finding them fascinating.

[J N Winkler]

Really you could say the same about much of the bridgework in the state in general.  There are so many examples of early 20th bridges in Arizona in relatively good repair whether they are on active roadways or not.

Arizona is apparently the only one of the fifty states in which humidity is routinely low enough that steel bridge girders do not have to be painted and weathering steel (Cor-Ten and the like) does not work as designed.

Of note regarding Interstate standards, the 1967 Highway Act mandated two things:  that shoulder widths be carried across bridges longer than 200ft, and that Interstate segments be built with 4 lanes regardless of low traffic forecasts.

In that connection, the Statutes at Large contain the full text (the US Code contains just the provisions that are chosen for codification, which are typically of general application only and do not include measures that are local or private in nature, e.g. citizenship grants or cancellation of the Somerset Freeway):

Statutes at Large (GPO PDFs)

I have long had an interest in how the various standards for the Interstates were determined and how they've changed over time. To that end, I've been trying to collect the various standards publications. I have 2005 and 2016, but I have not been able to get hold of a copy of the earlier ones, including what I think is the first one from 1956.

I have some experience pursuing a similar research question as part of graduate study, but for British motorways rather than the Interstates.  I have found that standards documents give a snapshot of the engineering consensus as it existed at a given point in time and, as such, are important primary source documents.  However, they do not show how the engineers involved reached that consensus.  The decision-making involved typically occurs in a committee or conference context, so the next step is to hunt for archival materials such as meeting minutes, unpublished reports, etc.  For BPR/PRA/FHWA, these are likely to be held at the main NARA facility in College Park.  AASHTO also has its own archives, which I have not visited but which I understand are accessible to employees of AASHTO member agencies.  I would expect that outside guest access would be fairly simple to negotiate.

The process of setting standards for highway design (not just Interstates) is one of choosing positions on various constraint graphs that reflect the broadest acceptance it is considered feasible to attain.  The constraint graphs generally have hockey-stick curves and the challenge is to pick a position as near to the bend in the stick that can be attained at reasonable cost.  For example, research tends to show that accident risk stays flat for horizontal curvature ranging from 0° to 2° and then begins climbing between 2° and 3° and climbs more steeply after 3°.  Britain settled on 2° but has no mountains in the areas where motorways were being considered.  We settled on 3° and do have mountains.  Another example:  cars and trucks can treat grades of up to 3% the same, but as grade steepens past 3%, the spread in speed between cars and trucks widens.  Again, Britain settled on 3% (exceptionally 4% for hilly terrain, such as that encountered in the Pennines--M62 corridor--between Leeds and Manchester), while we finessed the issue by creating separate design classes according to terrain type and allowing up to 6% in the mountains.

A contemporary secondary-source reference such as Lawrence Hewes' American Highway Practice (1942) (your nearest university library probably has a copy) is very useful for researching the cost-versus-function tradeoffs inherent in setting design standards as those tradeoffs were understood when Interstates were first conceived.

A further generalization that applies to geometric design standards everywhere, not just in the US, is that changes between different generations of standards for the same type of facility tend to be greater for the earlier generations than for more recent ones.  As a result, there is potentially more difference between an Interstate built in 1960 and one built in 1980 than there is between the 1980 Interstate and another built in 2000.  There are two things going on.  As the knowledge base accumulates, further advances tend to be incremental.  Moreover, as traffic beds in and starts to accumulate, agencies tend to find that initial compromises to save on capital cost are dwarfed by the ongoing losses from accidents and delay, especially since the capital available for renewal tends not to be as large as envisaged at the time of initial construction (most of the network was built to a 20- to 25-year planning horizon, yet many original miles are still in service 50 to 60 years later).

[roadman65]

Was changes ever made over time?  Being that the use of Future interstates where in the past substandard roads were allowed to be signed as such.

I-295 in NJ and most of I-78 in PA come to mind as those were allowed to be signed as even though the road lacked certain qualities for full interstate freeway.

[PHLBOS]

Was changes ever made over time?  Being that the use of Future interstates where in the past substandard roads were allowed to be signed as such.

I-295 in NJ and most of I-78 in PA come to mind as those were allowed to be signed as even though the road lacked certain qualities for full interstate freeway.

If you're referring to the stretch of I-295 where US 130 is concurrent with it.  That stretch underwent a major upgrade (to modern Interstate standards) at least 25 years ago.