Caltrans 2015 Standard Plans

[jeffe]

Caltrans has updated the standard plans for 2015.  The last update was in 2010.  There really aren't a lot a major changes, mostly just clean up, based on the summary:

http://www.dot.ca.gov/hq/esc/oe/project_plans/highway_plans/stdplans_US-customary-units_15/viewable_pdf/note/2015_SP_DIGEST_OF_CHANGES.pdf

I thought there might be some updates such as: overhead sign mounting for external tabs, a standard lane line detail combining Botts dots and thermoplastic, a signal mast arm that allows for more signal heads, etc.  But instead, it seems like the main purpose of this update is to just rollup all of the incremental changes that have been made since 2010.

[roadfro]

That's too bad that they haven't incorporated some of these things... For the signal poles (and possibly external exit tab detail), they could probably borrow heavily from Nevada.

I'd hazard the guess that Caltrans is going to hold out on external exit tabs as long as FHWA lets them. If having internal tabs has worked to get Caltrans (moving towards) substantially conforming to MUTCD exit numbering requirements, FHWA probably won't press the issue for a while.

[myosh_tino]

I thought there might be some updates such as: overhead sign mounting for external tabs

I don't think a detail for mounting external tabs probably will come out until the old sign trusses are taken out of service.  The old trusses do not adhere to the current wind-loading standards set by AASHTO.

a standard lane line detail combining Botts dots and thermoplastic

I'm not sure if this is necessary as all it would entail is combining Laneline Details 12 and 13.  The combination of botts dots and thermoplastic striping has been a fairly common practice in the S.F. Bay Area for quite some time.

a signal mast arm that allows for more signal heads, etc.

The most signal heads I've seen is 4 on a mast arm.  How many more do you need?

[vdeane]

I thought there might be some updates such as: overhead sign mounting for external tabs

I don't think a detail for mounting external tabs probably will come out until the old sign trusses are taken out of service.  The old trusses do not adhere to the current wind-loading standards set by AASHTO.

Nevada seems to do fine with the exact same structures.

[nexus73]

I'm still waiting to see how long it takes to put up I-210 signage on the SR 210 section. 

Rick

[jakeroot]

I'd hazard the guess that Caltrans is going to hold out on external exit tabs as long as FHWA lets them. If having internal tabs has worked to get Caltrans (moving towards) substantially conforming to MUTCD exit numbering requirements, FHWA probably won't press the issue for a while.

Is there any particular reason the FHWA would crack down on them? I've never really seen a difference between what California does, and what Washington or Illinois do, beyond aesthetic preferences for either using the entire width of the sign or just part of it.

*Edit: To clarify, I don't see the placement of the exit tab as a matter of function, but rather of aesthetic preference.

[jeffe]

I don't think a detail for mounting external tabs probably will come out until the old sign trusses are taken out of service.  The old trusses do not adhere to the current wind-loading standards set by AASHTO.

That's a good point about the old sign trusses not being able to handle external tabs due to wind loading issues.  However, the redesigned trusses do, so the detail would only apply to the newer signs.

I don't really have any issue with internal tabs, except some signs are crowded so the internal tab is reduced in size or not used at all.  Having the option to add an external tab in that case would be useful.

I'm not sure if this is necessary as all it would entail is combining Laneline Details 12 and 13.

This is more about standardizing the various practices of different Caltrans districts.  San Diego specifies the lines as 11/13 as you noted.  However, Los Angeles uses a custom 13M (modified) detail that is illustrated on each project plan.  The Bay Area also uses a custom 13M specified on project plans, but it is different from the one used in LA.

The most signal heads I've seen is 4 on a mast arm.  How many more do you need?

The most the standard plans allow is three signal heads; usually one left turn signal and two through signals.

Case 5 signal loading:
http://www.dot.ca.gov/hq/esc/oe/project_plans/highway_plans/stdplans_US-customary-units_15/viewable_pdf/es-07g.pdf

Santa Clara County, however, does use mast arms with 4 signal heads in some locations on the County Expressways.  This may be the signals to which you are referring.  I'm not sure if those are a custom design or if the county just determined that the wind loading was not an issue in those areas.

As for how many are needed, if a signal head per lane policy was adopted, then quite a few more would be required.  Even without such a large increase, one or two more signal heads could prove to be useful.  For example, locations with a triple left turn usually only have one overhead left turn signal.  An additional signal head would help in a situation like this.

[roadfro]

I'd hazard the guess that Caltrans is going to hold out on external exit tabs as long as FHWA lets them. If having internal tabs has worked to get Caltrans (moving towards) substantially conforming to MUTCD exit numbering requirements, FHWA probably won't press the issue for a while.

Is there any particular reason the FHWA would crack down on them? I've never really seen a difference between what California does, and what Washington or Illinois do, beyond aesthetic preferences for either using the entire width of the sign or just part of it.

*Edit: To clarify, I don't see the placement of the exit tab as a matter of function, but rather of aesthetic preference.

The FHWA probably cracked down on Caltrans to implement the CalNExUs numbering system in the first place, as the last state to implement exit numbering period. If Caltrans' current exit number designs are in their state MUTCD, which has to be in 'substantial conformance' with the national version, then I imagine FHWA is happy enough with the internal tabs for now.

For the record, I don't see a big issue with the internal exit tabs in most cases. But in those cases where the sign uses reduced letter sizes or eliminates message elements in order to get the exit tab to fit, that's where I find the issue and feel external tabs would be beneficial.

[jrouse]

The external tab design is not a high priority for Caltrans' structural engineers.  For now, if they are needed on a project, a special design is developed.   I believe that a standard design could be put together pretty easy, using either the special details that they've done for past projects, or putting together something new.  I would agree that the wind loading issue with the older trusses is probably another reason why a detail hasn't been developed.   

Someone mentioned the detail that Nevada uses.  From what I've seen, that detail involves using a sign panel frame and formed sign panels.  While some districts use frames and formed panels (District 4 uses them a lot),  not all of them do.  I believe that type of sign design is probably a bit more expensive, and it's not conducive for tubular sign structures either.  So an alternative needs to be available.


iPhone

[SignBridge]

Re: the above query on how many signal heads are needed on mast arms, it's not uncommon in eastern states (and Colorado) to have as many as five. Typically 3 will be over 3 thru lanes and 2 left-turn heads over 2 left-turn lanes. In a perfect installation they would all be 12 feet apart which usually looks about right, but sometimes they are located closer together which always looks goofy. However the Manual does allow a minimum of only 8 feet between the 2 required heads, though as I said it usually looks bad.

And re: California's internal exit tabs, I don't think it's a wind-loading issue. These things usually come down to economics. Less hardware needed, so they save money on a large scale statewide.

[roadfro]

Re: the above query on how many signal heads are needed on mast arms, it's not uncommon in eastern states (and Colorado) to have as many as five. Typically 3 will be over 3 thru lanes and 2 left-turn heads over 2 left-turn lanes. In a perfect installation they would all be 12 feet apart which usually looks about right, but sometimes they are located closer together which always looks goofy. However the Manual does allow a minimum of only 8 feet between the 2 required heads, though as I said it usually looks bad.

The current Nevada standards install one overhead sign head per lane (plus a far side pole mount). So in the Las Vegas area it is not uncommon to see 5 or 6 signal heads on one mast arm, and this is becoming increasingly common in Reno area as well. The NDOT standard plans have a max mast arm length of 60 feet, although longer arms are used in some cases that may need special designs.

Nevada (at least the Reno-Sparks and Carson City areas) older standards had the similar curved mast arms that are very similar to the Caltrans specs (I haven't seen any new installations with curved mast arms in quite some time). he newer poles have thicker diameters which are sturdier and seem to support longer lengths and more signal heads.

[jakeroot]

The newer poles have thicker diameters which are sturdier and seem to support longer lengths and more signal heads.

It's funny how math works. I would have though thicker poles would be more top heavy, but I suppose it's all about the mast mounting than pole thickness (lol).

[roadfro]

The newer poles have thicker diameters which are sturdier and seem to support longer lengths and more signal heads.

It's funny how math works. I would have though thicker poles would be more top heavy, but I suppose it's all about the mast mounting than pole thickness (lol).

The newer mast arms are thicker at the base but taper down to a narrower diameter towards the end. The older poles seem to be a bit closer to a uniform diameter, from what I observe. I imagine that has something to do with it.