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Interstate Freeway Overpass Height

Discussion in 'General Technical Questions and Answers' started by KB6OIN, Nov 20, 2009.

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  1. KB6OIN

    KB6OIN Ham Member QRZ Page

    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. AB3KP

    AB3KP XML Subscriber QRZ Page


    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.

  3. N3XP

    N3XP Ham Member QRZ Page

    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. K0RGR

    K0RGR Premium Subscriber QRZ Page

    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.
  5. W6ABZ

    W6ABZ Ham Member

    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. KE5YXD

    KE5YXD Ham Member QRZ Page

    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.
  7. K4JC

    K4JC Ham Member QRZ Page

    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: Nov 20, 2009
  8. W8ZNX

    W8ZNX Subscriber QRZ Page

    for a year or two worked part time for a boat hauling co
    its been years since i drove for a living
    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

    dit dit
  9. K9XR

    K9XR Ham Member QRZ Page

    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.

  10. W0IS

    W0IS Ham Member QRZ Page
  11. K8ERV

    K8ERV Ham Member QRZ Page

    Tidbit: My home town had a RR overpass that went over a sharp dip in the road. The clearance was marked propery to the road directly below. But a long semi would stretch acrsoss the dip and be much higher. About every two years one would get hung up. Fortunately the RR tracks were not harmed.

    Don't raise the bridge, let the air out of the tires. (Jerry Lewis).

    TOM K8ERV Montrose Colo
  12. WC5B

    WC5B XML Subscriber QRZ Page


    13'6" is your lowest height on the ENTIRE "INTERSTATE" system(Not to include all US and State Hwys, Just I- this and I- that). The one exception is the right hand lane of (I believe) I-70 in Downtown St. Louis. They may have fixed that though. Its never been an issue. Many New England and Chicago towns and highways have lower overpasses, but interstates are not effected. If you need to go higher then 8 or 9 feet off of the interstate, I would stop at any truck stop and check out the commercial vehicle atlas that they all sell. In the front will be a state by state, road by road height list.

    Note that you will mostly see overpasses 14-16feet clearance, but 13'6" is the designed limits.
    Last edited: Nov 20, 2009
  13. KA9MOT

    KA9MOT Ham Member QRZ Page

    There are many overpasses in the 12 foot range on Interstate highways in Urban areas. New York and Chicago especially. Spend 20 bucks and buy a truckers atlas at a truckstop. That will tell you about low overpasses and where they are.

    Not knowing where you were starting from in NYC, I have to wonder why I-78? You'd be better off getting on I-80 in the city or taking I-280 up to 80. I-78 sux.

    This time of year, and from where you are going to be coming from, you might consider a southern route. The mountains in Wyoming, Utah, or Colorado are gonna suck. Good possibility of snow and ice and 80 MPH winds in the high passes.

    Drop down to I-70 to St,Louis, Pick-up I-44 to Oklahoma City, then I-40 over to Kingman, AZ where you'd pick up US-93 up to Vagas plus you would get to cross Hoover Dam. A few more miles, but allot safer.
  14. WC5B

    WC5B XML Subscriber QRZ Page

    False, 13-6 is as low as they go on the interstate (aside from that one lane in STL). Period!

    Surface streets are a different story. This includes US and State Hwy's. Thats where you have to be careful under 13-6.

    Other then that... I agree completely with swing south. It is much less painful this time of year, and only a few hours longer. Just remember that I-44 is a toll road in Oklahoma, but not much for a car. If you wanted to skip it, swing south at Joplin on US78?, down I-540 through Fayetteville, AR and pick up I-40 in Ft. Smith. That's for adventure of course, but its a real pretty drive. NW Arkansas is pretty breathtaking IMOP.

    18 Wheeler Mobile.
    Last edited: Nov 20, 2009
  15. AI3V

    AI3V Ham Member QRZ Page

    Do they still have restrictions on the Hoover dam about what you can drive across or have as cargo?

    According to This website somebody will be wanting to look in the truck.......

    Last edited: Nov 20, 2009
  16. WC5B

    WC5B XML Subscriber QRZ Page

    Cars and RVs should be fine, but there is still a ban on Semi's since 9/11.
  17. K4JC

    K4JC Ham Member QRZ Page

    Sorry, NO trucks, including rental trucks, are allowed across Hoover Dam. I had to use the I40-AZ68-NV163-US95 route to Las Vegas many times when I was on the road!
  18. WC5B

    WC5B XML Subscriber QRZ Page

    Kinda scary really. If its that strict, it makes you think they may have had a lead or something. World is nutz lately.
  19. K0RGR

    K0RGR Premium Subscriber QRZ Page

    Maybe not a lead, just a premonition. An explosion on the dam could do some serious damage!
  20. KB5SXC

    KB5SXC Ham Member QRZ Page

    I-80 East Coast to the West.

    Good choice, Ohio, and the Gary, IN./Chicago, IL areas are a bit of a drag. But all in all I-80 is a Good Drive, Drove it many time in a Big Rig, Freightliner and Mack. Off Hand, I don't remember anything under 14 ft. of Clearance on that route. And the Laptop that I have all of my Route programs on is out of juice, and the charger is belly up. I always scheduled my runs to sleep before Chicago Area, and to pass throught that section of 80 at around 01:00 AM. Makes for the fewest traffic tie-ups which can be a Bear in that section of 80. I would recommend You get a Rand-McNally Motor Carriers Atlas. Plus a Truck Stop Guide. Both of these might be found online or at a larger Truck Stop. Flying J, Petro, T/A, usually decent Truck Stops. Run I-80 to Salt Lake City, I-15 to Las Vegas.
    Last edited: Nov 21, 2009
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