AARoads Forum

National Boards => General Highway Talk => Traffic Control => Topic started by: roadman65 on October 02, 2019, 08:53:46 PM

Title: Full Gantries where partial bridge or mast arm will do
Post by: roadman65 on October 02, 2019, 08:53:46 PM
https://www.flickr.com/photos/54480415@N08/45493212364/in/album-72157675874106048

As you can see this structure was not needed completely.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: sprjus4 on October 02, 2019, 09:18:58 PM
VA-168 Southbound Exit 8 in Chesapeake, VA. (https://www.google.com/maps/@36.6632798,-76.2304549,3a,37.5y,179.43h,85.33t/data=!3m6!1e1!3m4!1s5vcn5bqF17bABQNTGSF05Q!2e0!7i16384!8i8192)

Seemed to do it just fine further north at Exit 10 (https://www.google.com/maps/@36.6935808,-76.2277735,3a,75y,190.39h,82.84t/data=!3m6!1e1!3m4!1s6QazRvsKaJfE8jf_Qd4y0w!2e0!7i13312!8i6656)
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: Ian on October 02, 2019, 09:34:17 PM
Quote from: roadman65 on October 02, 2019, 08:53:46 PM
https://www.flickr.com/photos/54480415@N08/45493212364/in/album-72157675874106048

As you can see this structure was not needed completely.

I notice that the empty space on the structure includes an extended catwalk with abandoned sign lights, which makes me think that there was once a sign present in said empty space. Either that, or MoDOT planned on installing a sign there, but never did.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: sprjus4 on October 02, 2019, 09:44:43 PM
Quote from: Ian on October 02, 2019, 09:34:17 PM
Quote from: roadman65 on October 02, 2019, 08:53:46 PM
https://www.flickr.com/photos/54480415@N08/45493212364/in/album-72157675874106048

As you can see this structure was not needed completely.

I notice that the empty space on the structure includes an extended catwalk with abandoned sign lights, which makes me think that there was once a sign present in said empty space. Either that, or MoDOT planned on installing a sign there, but never did.
Nothing there, even as far back as 2008.

https://www.google.com/maps/@38.7772268,-90.3526721,3a,75y,334.38h,82.14t/data=!3m6!1e1!3m4!1sw36iURCWCD4Tduv0kFhITQ!2e0!7i3328!8i1664
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: JoePCool14 on October 03, 2019, 06:37:08 PM
Here's one on the IL-WI border on I-94:

(https://i.imgur.com/4hfwiFn.png)

I think this may have been a contractor mistake when the Russel Road and US-41 exits were rebuilt a few years ago. Not sure what they were thinking here.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: roadman on October 07, 2019, 12:47:22 PM
Quote from: sprjus4 on October 02, 2019, 09:18:58 PM
VA-168 Southbound Exit 8 in Chesapeake, VA. (https://www.google.com/maps/@36.6632798,-76.2304549,3a,37.5y,179.43h,85.33t/data=!3m6!1e1!3m4!1s5vcn5bqF17bABQNTGSF05Q!2e0!7i16384!8i8192)

Seemed to do it just fine further north at Exit 10 (https://www.google.com/maps/@36.6935808,-76.2277735,3a,75y,190.39h,82.84t/data=!3m6!1e1!3m4!1s6QazRvsKaJfE8jf_Qd4y0w!2e0!7i13312!8i6656)

To provide a cantilever support for the signs at Exit 8 would require a cantilever arm approximately 62 feet in length.  While such a structure could be designed, it is unlikely that most steel fabricators could provide an upright pole with the necessary wall thickness.  Providing a full span structure with the left upright in the median would also require guardrail or other protection for the sign structure, whereas extending the span across the full width of the roadway puts both uprights behind existing guardrail.

By contrast, the cantilever arm on the support at Exit 10 is only about 38 feet long.  For such sign supports, most DOTs consider the practical limit for arm length to be 40 feet.  Again, this is due to fabrication constraints with the support uprights and constructability considerations for the foundation.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: jbnv on October 07, 2019, 04:39:19 PM
I passed under this one (https://www.google.com/maps/@30.453596,-90.9617475,3a,75y,83.35h,85.87t/data=!3m6!1e1!3m4!1sfNVxV9otyYcTzJnkQfn9GA!2e0!7i16384!8i8192) just a few hours ago.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: ErmineNotyours on October 08, 2019, 07:46:24 PM
Since removed for construction of a light rail line in the carpool lanes, this pair (https://goo.gl/maps/fuQqKEAm4s5He27U6) has one gantry over just the main line, and one over both the carpool lanes and the main line.

This one (https://goo.gl/maps/s46b9SuH84BjuZGW8) used to have a full gantry for just the HOT lane toll information sign, but they've since added the "Lane ends, merge left" sign on the right.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: ozarkman417 on October 19, 2019, 11:26:17 PM
Recently passed under this one (https://maps.app.goo.gl/8a2Zok1pWaye5dVFA)

SM-G965U

Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: fwydriver405 on October 20, 2019, 11:51:09 AM
There are two in Manchester, NH that I know of on the Granite St exit off on I-293/Everett Turpike:
Southbound (https://www.google.com/maps/@42.9897264,-71.4714251,3a,25.7y,193.89h,91.95t/data=!3m6!1e1!3m4!1stuBOONpIpNqaZjVyGv46Hg!2e0!7i13312!8i6656)
Northbound (https://www.google.com/maps/@42.98044,-71.4700842,3a,55.2y,21.24h,90.36t/data=!3m7!1e1!3m5!1svDaNnMqyyQNpOgElWn8UAQ!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DvDaNnMqyyQNpOgElWn8UAQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D239.38666%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656)
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: Big John on October 20, 2019, 12:20:41 PM
Georgia will not accept new cantilever gantries.
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: marleythedog on October 20, 2019, 07:13:28 PM
I-75 South exit 74 (https://www.google.com/maps/@40.0632479,-84.233038,3a,75y,187.99h,96.22t/data=!3m6!1e1!3m4!1suPi86OLLM4CcLWnnm1Aylw!2e0!7i16384!8i8192) has full gantries at 1/2 mile and exit point that are unnecessary. This exit used to be A/B southbound (parclo B3?), so there used to be two signs at these points. However, at the same time that 75 was widened, the loop ramp was dropped to make a standard diamond, and the gantries erected then have never had two signs on them.

I-75 South exit 41 (https://www.google.com/maps/@39.6011728,-84.2370662,3a,75y,215.61h,78.48t/data=!3m6!1e1!3m4!1ssRC0vLUABKRpVIUHuAxCRw!2e0!7i16384!8i8192) (also at 1/2 mile and exit point) - This seems like something they should have been able to do with a partial bridge. I wonder if they were contemplating pull-thru signs here because I-675 has just merged in?
Title: Re: Full Gantries where partial bridge or mast arm will do
Post by: roadman on October 21, 2019, 02:01:20 PM
Quote from: Big John on October 20, 2019, 12:20:41 PM
Georgia will not accept new cantilever gantries.

That's been that way since the mid-1980s after GDOT had some anchor bolt failures.