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Thread: Interstate Freeway Overpass Height

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  1. #1

    Default Interstate Freeway Overpass Height

    Howdy Hams. What is the LOWEST Overpass Height on Interstate Freeways? I will be driving a 26ft Long, and 12 Feet High U-haul truck from NYC, New York to Las Vegas Nevada. I will be taking my 2mtr handheld with me and wish to put my Hustler Mag Mount 2meter antenna on top of the container portion of this truck. With the truck being 12 feet high, the mag mount about 4feet,6 inches high, that would put it's ant. top as 16ft, 6 inches high. I noticed yesterday the over pass here in California on a state highway was 15 feet high. I could of course put the mag mount ant on the cab of the truck , but it would be blocked somewhat by the higher container part of the truck,behind the cab, and the wind created by driving, would push the ant part of the mag mount in such a way it would be touching the metal part of the container all the time. Any thoughts on this? I leave in two days. For the most part from NYC to Las Vegas I will be taking I 78,then I 81, then I80. Thanks,Jim KB6OIN

  2. #2

    Default

    From: http://en.wikipedia.org/wiki/Interstate_Highway_standards

    Vertical clearance. Minimum vertical clearance under overhead structures (including over the paved shoulders) of 16 ft (4.9 m) in rural areas and 14 ft (4.3 m) in urban areas, with allowance for extra layers of pavement. Through urban areas at least one routing should have 16 ft (4.9 m) clearances.


    -- If you do, I wouldn't want to be holding on to the HT.

    Matt

  3. #3
    Join Date
    May 2001
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    Undisclosed for my security
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    2,131

    Default

    Quote Originally Posted by KB6OIN View Post
    Howdy Hams. What is the LOWEST Overpass Height on Interstate Freeways? I will be driving a 26ft Long, and 12 Feet High U-haul truck from NYC, New York to Las Vegas Nevada. I will be taking my 2mtr handheld with me and wish to put my Hustler Mag Mount 2meter antenna on top of the container portion of this truck. With the truck being 12 feet high, the mag mount about 4feet,6 inches high, that would put it's ant. top as 16ft, 6 inches high. I noticed yesterday the over pass here in California on a state highway was 15 feet high. I could of course put the mag mount ant on the cab of the truck , but it would be blocked somewhat by the higher container part of the truck,behind the cab, and the wind created by driving, would push the ant part of the mag mount in such a way it would be touching the metal part of the container all the time. Any thoughts on this? I leave in two days. For the most part from NYC to Las Vegas I will be taking I 78,then I 81, then I80. Thanks,Jim KB6OIN
    It's not going to work. 16 feet is far too high, especially when you have to get off the highway for fuel, food and too spend the night. Also, good luck finding enough metal on the top of the box that a magnet will stick to.

    I would go with a 1/4 wave on the cab of the truck.

    Be careful on 78 in PA, it is one heck of a deadly road.

  4. #4
    Join Date
    Apr 2002
    Location
    Rochester, MN
    Posts
    20,515

    Default

    Assuming the truck has one, you could put it on the hood of the truck, too. Yes, it will be blocked to the rear. But that would be better than having it blow back into the trailer wall.

    We have one railroad bridge here on a state highway that's 13 feet, something. According to Wikipedia, the minimum overpass height in urban areas is only 14 feet for an Interstate highway.
    EchoLink, IRLP, Allstar and DSTAR linking - adding interest to repeaters worldwide 24X7

  5. #5
    Join Date
    Mar 2002
    Location
    Mountain View, California
    Posts
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    Default

    I’m in the SF bay area and before every over pass there is a highway sign stating the up coming overpass is 15 feet 1 inch high….( 1 inch?...whats up with that? )

  6. #6

    Default

    I thought overpasses only had to be 13ft 6in. That's what every overpass in this region of the country is. And typically, 18-wheelers and campers are designed to conform to 13'6" restrictions.
    KE5YXD

  7. #7
    Join Date
    Jan 2000
    Location
    Between the Port of Indecision and Southwest of Disorder
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    Default

    I manage a Budget Truck Rental dealership (along with multiple other duties!) and I can tell you a mag mount won't stick to the top of the box. It will work fine on the roof of the cab with plenty of clearance. I've done just that many times.

    By the way, most overpasses are actually 8" to 12" higher than they are marked, to accommodate those mavericks who will try to take a 14' high load under a 13'6" overpass!
    Last edited by K4JC; 11-20-2009 at 05:39 PM.
    AMBIGUITY - What happens in vagueness, stays in vagueness.

  8. #8

    Default

    for a year or two worked part time for a boat hauling co
    its been years since i drove for a living
    but
    max height without permit is 13.6

    it was loads of fun hauling a 45 ft sail boat
    that when loaded was 12 ft wide 16 ft high

    worst was a river queen house boat
    it was a two day job
    one day to load second day to move it 30 miles
    unloading took only 20 min

    there are drivers guides
    that tell where all the low clearance spots are

    most freight boxes are not made of steel
    the mag mount will not stick to freight box

    if the cab is made of steel use roof of the cab
    will work fb
    drove slick seat for a few years
    had a mag mound and a gutter clamp mount
    still sometimes would not work
    '" no gutter, cab not steel "
    duct taped the antenna to the mirror mount
    TR-7400 did not mind

    mac
    dit dit

  9. #9

    Default

    First of all there is a prettty good chance that the freight body on the truck is made of aluminum so that could be a problem. Some also have Fiberglass roofs with aluminum cross members.

    If you could get a magnet to stick on the top of the truck a quarter wave magnet mount would do a fantastic job and only be a couple of inches over the interstate height limit and should present no problem at all any where near the interstate except for maybe a low hanging tree.


    Quote Originally Posted by KB6OIN View Post
    Howdy Hams. What is the LOWEST Overpass Height on Interstate Freeways? I will be driving a 26ft Long, and 12 Feet High U-haul truck from NYC, New York to Las Vegas Nevada. I will be taking my 2mtr handheld with me and wish to put my Hustler Mag Mount 2meter antenna on top of the container portion of this truck. With the truck being 12 feet high, the mag mount about 4feet,6 inches high, that would put it's ant. top as 16ft, 6 inches high. I noticed yesterday the over pass here in California on a state highway was 15 feet high. I could of course put the mag mount ant on the cab of the truck , but it would be blocked somewhat by the higher container part of the truck,behind the cab, and the wind created by driving, would push the ant part of the mag mount in such a way it would be touching the metal part of the container all the time. Any thoughts on this? I leave in two days. For the most part from NYC to Las Vegas I will be taking I 78,then I 81, then I80. Thanks,Jim KB6OIN

  10. #10

    Default

    Quote Originally Posted by W6ABZ View Post
    I’m in the SF bay area and before every over pass there is a highway sign stating the up coming overpass is 15 feet 1 inch high….( 1 inch?...whats up with that? )
    The Low Clearance (W12-2) sign (see Figure 2C-3) shall be used to warn road users of clearances less than 300 mm (12 in) above the statutory maximum vehicle height. Guidance: The actual clearance should be shown on the Low Clearance sign to the nearest 25 mm (1 in) not exceeding the actual clearance. However, in areas that experience changes in temperature causing frost action, a reduction, not exceeding 75 mm (3 in), should be used for this condition. Where the clearance is less than the legal maximum vehicle height, the W12-2 sign with a supplemental distance plaque should be placed at the nearest intersecting road or wide point in the road at which a vehicle can detour or turn around.
    http://www.ricesigns.com/buy/overhea...ance_signs.htm

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