# Caution: Water Sprays While Testing **URL:** \ **Category:** Factual Questions\ **Created:** [August 8, 2007, 9:31pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920 "2007-08-08T21:31:12Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Drum\_God](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drum_god/32/44_2.png) [@Drum\_God](https://boards.straightdope.com/u/Drum_God)\ **Post date:** [August 8, 2007, 9:31pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/1 "2007-08-08T21:31:12Z")
This morning, I was driving along a local state highway when I passed a trailer with the above referenced warning on it. The trailer was being towed by a TxDOT vehicle. The trailer was small with a single axle and was traveling about 50 miles per hour (in a 70mph area). A nozzle in front of the left wheel on the trailer would spray water (I presume) onto the road in front of the wheel. As promised by the warning, water would spray up from under the wheel. The resulting water patch would be about fifty feet long. Judging from the splotches of water I drove over before overtaking this machine, it had been spraying these patches of water for many miles. What might TxDOT have been testing in this way? ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [August 8, 2007, 10:07pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/2 "2007-08-08T22:07:30Z")
Wet traction of various pavements? ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [August 8, 2007, 11:03pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/3 "2007-08-08T23:03:31Z")
Possibly they want to be sure to salt peoples cars in the summer too. They spray salt solution on ice instead of dropping salt. Yes even Texas freezes. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 8, 2007, 11:08pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/4 "2007-08-08T23:08:19Z")
[QUOTE=Kevbo] Wet traction of various pavements? [/QUOTE] Pretty much. [Skid testing](http://www.hwycontractor.com/articles/oct03b.htm): > [@](#): > > For existing pavements, specialized friction testing equipment is available to government agencies or consulting engineers, and skid numbers can become an important part of a pavement management system. Each state highway department maintains one or more pavement friction measurement systems that continuously monitor their pavements for developing slippery spots, the Texas group says. > > “These systems test the pavement by using a trailer, pulled by a truck at 40 miles per hour,” the Institute reports. “One wheel of the trailer is locked, for a few seconds, while water is applied just ahead of it. The drag force is accurately measured, using electronic instruments. The friction is calculated by dividing the drag force of the wheel by the weight of the wheel, simple high school physics.” ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [August 8, 2007, 11:09pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/5 "2007-08-08T23:09:55Z")
So is there a chance of them skidding sideways? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 8, 2007, 11:18pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/6 "2007-08-08T23:18:57Z")
[QUOTE=Harmonious Discord] So is there a chance of them skidding sideways? [/QUOTE] In the absence of a lateral force to cause them to do so, no. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [August 9, 2007, 12:12am UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/7 "2007-08-09T00:12:05Z")
[QUOTE=Q.E.D.] In the absence of a lateral force to cause them to do so, no. [/QUOTE] Even if only \*one \* wheel of the trailer is locked? I’m having a hard time figuring out the physics but I can’t imagine a trailer with two free-rolling wheels behaves the same way as one with one of the wheels locked. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 9, 2007, 1:07am UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/8 "2007-08-09T01:07:30Z")
[Model SFT5041 and SFT5042 Pavement Skid Friction Test Systems](http://www.intlcybernetics.com/friction_tester.htm) [Standard Test Method for Determining Longitudinal Peak Braking Coefficient of Paved Surfaces Using a Standard Reference Test Tire](http://webstore.ansi.org/RecordDetail.aspx?sku=ASTM%20E1337-90(2002)) ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [August 9, 2007, 2:00am UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/9 "2007-08-09T02:00:23Z")
[QUOTE=Harmonious Discord] Possibly they want to be sure to salt peoples cars in the summer too. They spray salt solution on ice instead of dropping salt. Yes even Texas freezes. [/QUOTE] In all my 43 years of living in Central Texas I have never seen them spread salt during freezes. Sand is the preferred medium. Even then, since freezes are rare, there are never enough trucks ( or sand ) to get all the bridges covered in time. This, this along with the fact that Texas drivers freak out when the road is merely wet, let alone iced, makes driving here during a freeze the equivalent of sprinting through a minefield. ---
**Author:** ![Drum\_God](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drum_god/32/44_2.png) [@Drum\_God](https://boards.straightdope.com/u/Drum_God)\ **Post date:** [August 9, 2007, 3:17am UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/10 "2007-08-09T03:17:30Z")
[QUOTE=Harmonious Discord] Possibly they want to be sure to salt peoples cars in the summer too. They spray salt solution on ice instead of dropping salt. Yes even Texas freezes. [/QUOTE] Huh? The weather this summer has been really strange around here, but not ice-age strange. It very rarely freezes even in January, let alone August! I have never seen TxDOT or anyone else use salt on the roads in Central Texas. Maybe in north Texas, but I doubt it. Around here, one snowflake causes everything to shut down. **Q.E.D.** , thanks for the info. I had thought it might be something like that, but I wasn’t sure. The thought of locking the wheel as it’s rolling is certainly something that hadn’t occurred to me. ---
**Author:** ![Duke\_of\_Rat](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Duke\_of\_Rat](https://boards.straightdope.com/u/Duke_of_Rat)\ **Post date:** [August 9, 2007, 1:35pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/11 "2007-08-09T13:35:17Z")
[QUOTE=UncleRojelio] In all my 43 years of living in Central Texas I have never seen them spread salt during freezes. Sand is the preferred medium. Even then, since freezes are rare, there are never enough trucks ( or sand ) to get all the bridges covered in time. This, this along with the fact that Texas drivers freak out when the road is merely wet, let alone iced, makes driving here during a freeze the equivalent of sprinting through a minefield. [/QUOTE] In all those years you’ve never made it into the Panhandle, I guess. It’s not uncommon for the roads here to freeze over for days, even weeks, yet we are still able to…get ready…drive. Without freaking out. That said, sand and/or potash seems to be the spread of choice for intersections and bridges/overpasses. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [August 9, 2007, 1:56pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/12 "2007-08-09T13:56:01Z")
[QUOTE=Duke of Rat] In all those years you’ve never made it into the Panhandle, I guess. It’s not uncommon for the roads here to freeze over for days, even weeks, yet we are still able to…get ready…drive. Without freaking out. That said, sand and/or potash seems to be the spread of choice for intersections and bridges/overpasses. [/QUOTE] So that’s where all the damn sand trucks are when we are having a freeze emergency down here. Oh, and I have in fact driven through Dumbass more than once. ---
**Author:** ![Duke\_of\_Rat](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Duke\_of\_Rat](https://boards.straightdope.com/u/Duke_of_Rat)\ **Post date:** [August 9, 2007, 2:32pm UTC](https://boards.straightdope.com/t/caution-water-sprays-while-testing/414920/13 "2007-08-09T14:32:27Z")
[QUOTE=UncleRojelio] Oh, and I have in fact driven through Dumbass more than once. [/QUOTE] Well, we won’t hold that against you. The roads might not even be paved yet there.