FAQs
Q1. Is
a K or Ka-band radar device on the IACP’s approved
list important?
A1. Ka-band requirement combined
with IACP listing requirement reduces choices to, perhaps,
1 manufacturer in the US. Every sign manufacturer in the
U.S. but one uses one of two guns; Decatur Electronics SI-II
or Kustom Signals' DRU unit. Both of these are K-band units
designed expressly for this type of application but both
of no interest to the folks compiling the IACP list. Unless
the client expects to write tickets and issue fines for offenses
using these signs (not recommended either) this requirement
is competition limiting, over-reaching and costly. These
types of signs are described by both the NHTSA and the MUTCD
as "advisory" signs and not "traffic control" devices
negating any reason to over-engineer such a product.
Q2. The
sign we are considering has what they call a 7-Segment display.
They say these are as good as your full graphic characters?
Are they really?
A2. The seven segment style
design is simply antiquated. Moreover, independent studies
have shown that cognitive recognition of seven segment vs.
full graphic characters is significantly slower and at X-whatever
mph, time is of the essence. This independent study also
demonstrates that our 18" graphic display outperformed
one competitor's 25" character sign in live on-road
testing. The most recent revision of the California MUTCD
specifically recommends use of full graphic characters over
7 segments when selecting a speed feedback sign.
Q3. What
do you think of user adjustable amperage (sic. Intensity)
for different applications?
A3. There are no different
applications; every time you place one of these signs in
public you are trying to slow people down. Adding this variable
is only going to exasperate anyone looking for consistent
results. Now, automatic adjustment to ambient light conditions
is critical as you need full intensity in full sun and need
to moderate brightness for night conditions.
Q4. One
supplier is touting the advantage of a rather limited (30
degrees) included angle of readability. RU2 talks about 160+
degrees of legibility. What gives?
A4. This 30 degree thing is
like a religious question; you either believe or you don’t.
But once you do the trig, it smells more like a red herring.
Here is our take:
IF you calculate the distance
from the center of the sign face, accepting that the near
lane driver is something like 14 ft. lateral off-set and
intersect the driver with the 30 included angle the sign
goes dark for him about 52 ft. down range. If you open that
up to 160 included angle the sign goes dark about 2½ ft.
down range –let’s call it a 50 ft. delta. 50
feet at 35 mph is covered in less than 1 second, at 25 mph
in 1.36 seconds. What we are suggesting here is that the
entire argument is…an excuse, not a feature.
Q5. Regarding
the radar device, they talk about programming the sensor
for distance and inclusion/exclusion of approaching/receding
targets. Huh?
A5. Let’s take these
things separately. Being able to adjust the sensor for distance
isn’t an inherently bad idea. Our original response was
to make the sensor independently adjustable to the sign face
in both X and Y axis so that the sensor paints an “area
of interest” much like pointing a flashlight while keeping
the sign’s “best face forward”. This is
in contrast to being able to make the sensor “stupider” but
still pointing at the moose on the horizon. RU2 recently added user adjustable sensitivity to our signs in 5 increments for the greatest degree of flexibility in set up.
Oddly enough there are few suppliers
out there still providing base equipment without single directional
(approach only) radar, making it instead an option that you
have to pay for. Our gun can pick up 8 discrete targets,
determine approach/recede and, sort by signal strength. And
we don’t charge extra, so there! We specifically filter
for the strongest, oncoming target –only. Under what
circumstances would you want to display receding targets
other than to confuse everyone looking at the sign?
Q6. Suspensions:
Leaf Spring vs. Torsion Bar; what’s the difference
and should I care?
A6. At the loaded weights
we are talking about (1000 pounds is a trifle in the trailer
world) the biggest difference between the two technologies
is a bit nicer ride (torsion) versus bullet proof (leaf).
You may have to replace a torsion bar suspension over the
life of the trailer; you probably won’t have to replace
a leaf spring. We went with bullet proof leaf springs; some
of our competitors went torsion claiming a gentler ride for
their (tender) electronics. So, should you care? Nope.
Q7. What’s
the deal about wet paint versus powder coat and can you do
either right or wrong?
A7. Without a lot of hot air
(get it?), a properly applied powder coat finish will outperform
any wet paint finish. Today, you will find wet paint finishes
only on the cheapest of equipment and we don’t mean
just radar trailers. And sometimes that’s alright if
the life expectancy of the piece of equipment is short by
its nature (think: arrow boards).
We employ a 2 part powder
coat system, first applying what is known as “high
zinc” epoxy primer which gets a partial bake, then a
polyester application over that. Epoxies alone are very chemical
resistant, great adhesion and impact resistance but typically
have very little resistance to UV rays and will “chalk” very
fast leaving a dull, smudgy, unattractive finish. Polyesters
by themselves don’t have the chemical resistance of
epoxies but are specifically formulated for outdoor equipment
and have strong UV resistance, staying bright and shiny for
years. Dirty metal, sharp edges and under or over curing
are the enemies of a good powder coat. Great prep and attention
to process detail prevent that.
Q8. While
we’re on paint, are any coatings really “graffiti
proof”?
A8. No, not really. What we
have been told by the manufacturer we use (Rohm & Haas)
is that the only Graffiti-proof coating is a secondary clear
overcoat which, unfortunately, due to a difference in coefficient
of expansion, will craze (crack) and trap dirt, eventually
causing the “object of concern” to look like crap
anyway. And it’s expensive. We can do it. We don’t recommend
it.
Q9. Batteries,
batteries, batteries…what should I know about batteries?
A9. Quite a bit, yet nothing…how
Zen! There are really two questions here; one, what is the
difference in battery technology and two, how long can I
go with your equipment between charges?
Our battery universe is divided
along the lines of battery construction. Currently, there
are three common lead-acid battery technologies: Flooded,
Gel, and AGM.
Flooded or Wet Cells are the most common lead-acid battery-type
in use today. They offer the most size and design options
and are built for many different uses. Typically, the cells
can be accessed via small ~1/2" holes in the top casing
of the battery so the user can replenish any electrolyte
the battery vented while charging the battery.
The plastic container used
for flooded cells will have one or more cells molded into
it. Each cell will feature a grid of lead plates along with
an electrolyte based on sulphuric acid. Since the grid is
not supported except at the edges, flooded lead-acid batteries
are mechanically the weakest batteries. They are also the
cheapest.
Gel Cells use a thickening
agent like fumed silica to immobilize the electrolyte. Thus,
if the battery container cracks or is breached, the cell
will continue to function. Furthermore, the thickening agent
prevents stratification by preventing the movement of electrolyte.
As Gel cells are sealed and
cannot be re-filled with electrolyte, controlling the rate
of charge is very important or the battery will be ruined
in short order. Furthermore, gel cells use slightly lower
charging voltages than flooded cells and thus the set-points
for charging equipment have to be adjusted.
Absorbed Glass Mat (AGM) batteries are the latest step in
the evolution of lead-acid batteries. Instead of using a
gel, an AGM uses a fiberglass like separator to hold the
electrolyte in place. The physical bond between the separator
fibers, the lead plates, and the container make AGMs spill-proof
and the most vibration and impact resistant lead-acid batteries
available today. Even better, AGMs use almost the same voltage
set-points as flooded cells and thus can be used as drop-in
replacements for flooded cells. Basically, an AGM can do
anything a Gel-cell can, only better. However, since they
are also sealed, charging has to be controlled carefully
or they too can be ruined in short order.
Gel and Absorbed Glass Mat
batteries are relative newcomers but are rapidly gaining
acceptance. There are some very compelling reasons to use
VRLAs (valve regulated lead acid):
•Gel and Absorbed Glass
Mat (AGM) batteries can dispense charge at a higher rate
than flooded cells due to their lower Peukerts exponent.
Deep-cycle Flooded Cells cannot deliver more than 25% of
their rated amp-hour capacity in amps without plummeting
Available Capacity.
•Virtually no gassing under normal operating conditions: Unlike flooded
cells, gel cells and AGMs are hermetically sealed and operate under pressure
to recombine the oxygen and hydrogen produced during the charge process back
into water.
•For every additional 15 degrees of heat over 77 deg F, lead acid battery
life (regardless of type) is cut in half (batteries self-destruct with time,
you can only slow that process).
•VRLAs can operate in any orientation (although you may lose some capacity
that way) and even if a container is broken, a VRLA will not leak. Proper (heavy
duty) battery restraints are a must, regardless of battery type.
•Gel cells and AGMs require no maintenance once the charging system has
been properly set up. No equalization charges (usually), no electrolyte to replenish,
no specific gravity checks, no additional safety gear to carry in order to protect
yourself. If you want to be anal retentive about VRLAs you can load test them.
However, proper charge control and protection is much more important with VRLAs
because once fried it is impossible to revive them.
•The higher charge efficiency of AGMs allows you to recharge with less energy:
Flooded cells convert 15-20% of the electrical energy into heat instead of potential
power. Gel-cells lose 10-16% but AGMs as little as 4%. The higher charge efficiency
of AGMs can contribute to significant savings when it comes to the use of expensive
renewable energy sources (wind generators, solar panels, etc.) as your charging
system can be 15% smaller (or just charge faster).
•While flooded cells lose up to 1% per day due to self-discharge, VRLAs
lose 1-3% per month.
•High vibration resistance: The construction of AGMs allows them to be used
in environments where other batteries would literally fall to pieces. This is
another reason why AGMs see broad use in the aviation and the RV industry.
RU2 uses gel cells on its Fast-6000 and Fast-600 models,
AGM on everything else. Enough about that!
The other issue, probably
more germane, is field autonomy or,
how long can I deploy the trailer between charging. Everything
else being even, the two primary factors in play are
current draw of the gun and sign and duty cycle. Overall
efficiency of the design can vary all over. RU2’s
primary 12”and 18”character signs draw 18
Watts peak, another manufacturer may be at 25W, another
even higher. The difference between 18 and 25 is a 28%
advantage right there. We typically see 7 to 10 days
of service from a fully charged trailers and under proper
circumstances, many of our solar assisted trailers are
virtually field autonomous requiring quarterly of semi-annual
charges to “top them off”. Amp hour figures
are by themselves meaningless.
Q10. The "SPEED LIMT" sign size on your Fast-375 isn't dimensionally to MUTCD standards. Are we going to be in violation if we use
it?
A10. Regarding the “non-standard”sizing
of the Fast-375 sign overlay, it stems primarily from the
origin of the underlying electronics. That is, early on we
decided to make the best “full graphic”character
sign we could at standard 18”character size for placement
on a radar trailer. This was long enough ago that the pole-mount
concept hadn’t been marketed by anyone yet. As we were
not looking to reproduce or adapt to anyone’s standard
sheet metal we started out with a blank sheet of paper and
ended up with a terrific sign with a 40”wide case.
Designing the typical R2-1 Speed Limit
Sign overlay for the nearest standard size (36”x 48”)
we maintained the 1 to 1.33 aspect ratio and ended up with
a 41”x 54.5”plaque. Non-standard perhaps, but
conforming.
An interesting thing comes up in all of
this and is particularly poignant if one was examining “standards”for
a reason “Not To Do Something”; The 18”character
specification (or 12”for that matter) defies all R2-1
standards. The standard character heights are 8”, 10”,
14”and, 16”. The 16”character is for the
48”x 60”sign, recommended for posted limits of
55MPH or greater. Strictly by these standards everyone in
this business is wrong. An 18”character on a 36”x
48”(or larger) sign should look really stupid (and
non-conforming) except…that it doesn’t. And
our characters look really good in our plaque.
By the way, in looking for 3rd party blessings,
the most recent California MUTCD issued this: “Guidance:
To the degree practical, numerals for displaying approach
speeds should be similar font and size as numerals on the
corresponding Speed Limit (R2-1) sign” which we naturally
take as a ringing endorsement of our “full graphic
characters” (vs. antiquated 7 segment).
Q11. We are in the process of writing specifications for the purchase of a radar speed trailer. One of our engineers is concerned with NCHRP 350 compliance as we intend to use it on an Interstate. What's the scoop?
A11. Trailers of this type are exempt from NCHRP - 350 Crash Testing. Even though they are a Type IV device, the FHWA has recognized that in order for them to meet NCHRP-350 requirements - they would need an Impact attenuator that would be bigger than the Trailers. Additionally in an attempt to make Changeable Message Signs (Full Size Trailers) NCHRP-350 compliant (in past testing), the "Roll Ahead" factor encountered after impact was unpredictable. In other words - you couldn't tell if the impact attenuator made the unit safer - more often than not the Trailer would still roll forward further than an unprotected trailer and often would wind up crossing adjacent lanes of traffic.
It was decided that trailer mounted equipment would be compromised by an attenuator in that it would be heavier, take up a larger footprint on the roadway, and present an operational problem in its field deployment (make it more complex to setup and remove from the roadway - resulting in Longer exposure in live traffic to the user).
After checking accident statistics (Nationwide) the FHWA could not find a number of reported accidents of Vehicles running into the trailer mounted equipment (Other than a few anecdotal occurrences of Drunk Drivers hitting trailers).
Their final decision said that the practices currently being used (putting the trailers behind guardrail and barrier walls where practical,or in the clear way - described as 30 feet off of the traveled portion of the highway, or if need required that the unit be placed on a shoulder, then the unit should have at least 1-2 feet of clearance to the live lane and it should have temporary traffic control devices - that is orange drums or cones used to form a taper in front of the trailer to highlight the placement of the trailer on a shoulder.
REF http://safety.fhwa.dot.gov/roadway_dept/road_hardware/nchrp_350/catg4.htm
Q12. Okay, that's great but, how about NCHRP compliance and the Pole Mounted products you offer?.
"I spoke to you yesterday about the “ABC” Department of Transportation requirement that these signs must meet"crash-worthiness" as defined in the National Cooperative Highway Research Program Report 350. You indicated that these devices are exempt from that requirement, and you have a copy of some literature you could send me on the subject."
A12. “My bad” on this, to a point. The Report 350 exemption is for Category IV, trailer mounted devices - please see A11 above.
However, the FAQ’s for Sign and Luminaire Supports would indicate that the burden of testing is not on the “mounted object or device” as it is on the support structure itself. Please see excerpt below, link to original source provided (red highlight mine).
Q: WE WANT TO ADD LIGHTS, A BATTERY, AND A SOLAR PANEL TO OUR
SCHOOL ZONE SIGN. DOES THE COMBINATION HAVE TO BE CRASH TESTED?
A. There are four factors that determine the acceptability of
breakaway supports:
- Stub height (Must be 4 inches or less. As this will not change with the addition of auxiliary hardware it will not be discussed further.)
- Vehicle velocity change / occupant impact forces. The addition of flashing lights and solar panels or
other auxiliary equipment will not likely affect the change in velocity experienced by the vehicle or its occupants unless it becomes substantial compared to the mass of the pole. Additional hardware attached at or above the sign will raise the center of gravity of the system slightly but since it is away from the base the breakaway features will still perform as intended. The overall mass of the pole, sign, and auxiliary equipment should not exceed 600 pounds
.
- Windshield penetration. Windshield damage was not a formal pass/fail criterion under the 1985 AASHTO Sign and Luminaire spec and we did not change this when we adopted Report 350 in 1994. However, windshield damage will be pass/fail evaluation criteria under the AASHTO MASH. If the auxiliary hardware is at or above the sign, the effect should be minimal.
- Roof crush. Roof crush up to 5 inches was permitted under NCHRP Report 350, but very few sign installations even approached that amount. (Luminaire poles weighing 1000# or more could easily fail this test.) The addition of more hardware could increase the risk under low speed impacts, but roof crush can be controlled by following the 600 pound weight limit mentioned above. Under MASH, roof crush will be limited to 3 inches maximum.
Safe placement of these types of devices on the sign also depends on the structure of the sign, the sign height, the type of vehicle impacting the sign, and the breakaway nature of the sign support when it is impacted. The conditions outlined above assume the sign pole is rigid and that the pole itself will not deform upon impact. Also the breakaway feature must be a slip base, frangible coupling system, or a cast aluminum transformer base – “base bending or yielding” systems such as u-channel posts, perforated square steel tube posts, or composite posts require full scale crash testing.
Source: http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/qa_bsls.cfm#q6
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