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. I am...
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Trailer
Size: Some things to consider
while looking at the trailer size (height, weight and length)
is visibility around the trailer when it is setup and when
it is in tow.
Weight: The weight of the
trailer can predict whether or not it is feasible to tow
with a squad car or not. Sometimes a trailer may be so heavy,
it can only be safely towed with a truck. Also, moving the
trailer around by hand may be a problem if it weights too
much. If a trailer is too light, it could fall victim to
high winds during bad weather.
Materials of Construction:
The base of a trailer is primarily made from steel of various
shapes and thickness. The enclosure that houses the components
are usually made of steel or fiberglass. A popular material
for building trailer bases is 1 ½ to 2 inch square
tubing 1/16 to 1/8 inch think. In comparison, 1 1/2 square
tubing 1/16 inch thick would be average duty, and a 2 inch
square tubing 1/8 inch thick would be very heavy duty.
Paint: Good paint is important
in order to get many years of good service from your radar
trailer and withstand the rugged use. Powder coating is one
method of achieving this goal. Powder coating is a thick
baked on paint that is very durable.
Axle: A heavy duty axle with
a weight capacity rating stamped on it to ensure quality
is important. When the trailer is being moved, the axle and
springs take most of the abuse so they should be of good
quality. Grease fittings on the hubs will make routine greasing
an easy task which will ensure longer bearing life. Tires:
Tire size is important depending on the trailer usage and
size. If the unit has a lot of highway travel or the trailer
is heavy, at least a 13 inch tire is needed. This is about
the size of a small car tire. A typical 13 inch tire size
will be written BR78-13. If the trailer is light enough,
then an 8 to 10 inch tire will be sufficient. The smaller
the tire, the less the cost of the unit. An 8 or 10 inch
tire is the same size that is used on a small boat or jet
ski trailer. These sizes are typically written 4.80/4.00-8.
Light Hookup: The connector
that plugs in from your tow vehicle to the unit for lights
needs to be considered. There are three commonly found connections:
four prong flat plugs, four prong round plugs, and five prong
round plugs. The type your vehicles are equipped with should
be specified to the radar trailer manufacturer. This will
take out the frustration when you receive your trailer, and
aren’t able to hook it up properly to your vehicle.
Hitch: There are two common
ball sizes, 1 7/8 and 2 inch. Again, this should be outlined
in your radar trailer specifications to the manufacturer.
Theft: There are various methods
of theft deterrents. Everything from locking a bar through
the wheels, to simply locking a leveling jack and alarm systems
are available. The things to remember when reviewing these
systems are how effective the method is and how cumbersome
and time consuming is it to the person setting up the unit.
If someone really wants to steal the trailer, they will find
a way, the theft deterrents are only there to make it more
difficult for them to steal.
Lifting Jacks: Lifting jacks
are used to both stabilize the unit and compensate for uneven
terrain when setting up the trailer. The most widely used
type is the jack screw. The jack screw can be permanently
mounted or swing down. The jack screw type has a handle on
the top that turns to lower and raise the jack. One disadvantage
to this type of jack is that the handle has to be turned
many times in order to lower and raise the jack. If you multiply
this times three or four jacks, setup becomes a very cumbersome
and time consuming process.
Another type of jack is a swing down jack which requires
a handle to pry down a slotted skid one notch at a time.
This is a much faster jack but the operator needs a strong
arm and lowering the jack is more difficult.
One very fast and convenient jack is an electric actuated
jack. This jack can be extended 24 inches in about 30 seconds.
When reviewing different jacks keep in mind the personnel
and situation in which the unit will be setup.
Display
Size: When evaluating the
displays size, what is important is the actual character
size. For example, an 18 inch display should mean 18 inches
from the top of the number to the bottom of the number. Display
size requirements depend on the normal usage and budget for
the unit. For higher speed area usage, 45 miles per hour
and up, the sign should be at least an 18 inch or larger
display. In residential areas and school zones, a smaller
12 inch and larger display would be sufficient. Method of
Display: There are two ways to make numbers for radar signs.
One method uses light and the other is by flipping segments
electro-mechanically. The preferred method is light. This
is done using a technology that has only in the last ten
years become cost effective and efficient. The light is generated
from high intensity LED’s (light emitting diodes).
LED’s are not light bulbs, but are diodes which are
very power efficient and by focusing with a lens creates
a very bright light. Unlike light bulbs, LED’s can
be turned on and off many times with extremely low percentage
of failure. Flipping segments electro-mechanically is not
very power efficient and has moving parts which creates frequent
failures.
Display Arrangements: There
are primarily two arrangements for creating number characters.
One is a seven segment display which creates a squared off
number using a different combination of lines, much like
a calculator. The other method uses several rows and columns
of dots. This array of dots is known as full matrix display.
A full matrix display is capable of creating rounded characters
that are more pleasing to the eye and easier to recognize
at a glance.
Night and Day Viewing: In
order to see LED’s during the day, they need to be
at full brightness. At night, the LED’s at full intensity
can be blinding to on coming traffic. The intensity can be
controlled using ambient light sensing and adjusting the
intensity of the LED’s accordingly. This is commonly
referred to as automatic intensity control.
Protective Cover: The display
needs to be protected by a transparent window. The most commonly
used form of protection is Lexan, which is very durable and
will not be penetrated by most objects, including bottles,
rocks and in some cases even bullets. The texture of the
outside surface should not be shinny, as the sunlight or
headlights create a glare, preventing the numbers from being
easily seen.
Radar Unit
Band: One of the higher frequency
band radar units should be used, K band or higher. K Band
has many advantages including it’s accuracy, and is
widely used by manufacturers.
Single Directional Radar:
Another important feature to consider is a single directional
radar unit. Single directional radar will only display the
speed of on coming vehicles, ignoring traffic traveling away
from the unit. This prevents on coming motorist from getting
mixed signals as they approach the sign.
Certified Radar Units: It
is important that the radar unit has the proper FCC certification.
Not all radar units are certified, and some states have different
regulations as to what is a “certified”radar
unit. If a certified radar unit is required, it is important
to communicate this to your sign manufacturer.
Power System
Charging: Unless a unit is
equipped with a solar panel, the radar unit will require
periodic recharging. This could range from charging every
day to every 30 days depending on the usage and power supply.
The radar sign usage will have to be taken into consideration
when shopping for a sign. It only takes a few batteries to
run a unit for a few days, but it takes many batteries to
run for 30 days. The battery will need replacing every three
years or so, make sure the unit is easily serviceable and
consider the cost of replacement batteries.
Batteries: Battery technology
has come a long way in the last few years, and there are
some very good batteries available. Deep cycle dry or gel
cell batteries are efficient and emit no hydrogen gas during
recharging. These batteries are higher in initial cost, but
have a longer life expectancy. Another type of battery is
a deep cycle lead acid battery that also has a layer of oil
in the battery. This is a very efficient battery and emits
a negligible amount of hydrogen gas during recharging. This
battery is lower in cost, and like the dry and gel cell batteries,
is less likely to have corrosion on the terminals due to
the presence of acid.
Solar Power: The use
of a solar panel or panels is a good way to make a unit
self-sustaining. Some things to consider are the cost and
effectiveness of solar power. The effectiveness depends
upon the power required as compared to the power supplied
by the solar panel, and the amount of sunlight available
in your region. Consider how long the unit needs to run
without sunlight to determine if solar power is a cost
effective power supply.
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