Association for Stock Car Auto Racing (NASCAR) car is an
amazing machine that pushes the physical limitations of
automotive engineering. Crafting one of
these cars is a meticulous task that takes dozens of
designers, engineers and mechanics who put in hundreds of
hours to perfect the car before it ever rolls onto a race
track. On the track, the driver shows off his professional
skills by directing this 3,400-pound (1,542-kg) machine around
an oval track at speeds that would terrify most people.
Click the buttons on the left to view safety
features built into NASCAR race cars (Needs Flash
For many, sitting at the helm of one of these custom-made
dream machines is an appealing notion. With 750 horsepower
under the hood, the cars have the ability to reach speeds of
more than 200 mph (321 kph). But being behind the wheel of
this car as it is spinning out of control on a high-banked
super-speedway at 180 mph (289 kph), heading directly into a
concrete retaining wall -- this is the sober reality that
professional drivers must face. Certainly, the tragic death of
seven-time NASCAR champion Dale Earnhardt at the 2001 Daytona
500 race increased everyone's awareness of the dangers of
professional car racing.
In an average street car equipped with air bags
and seatbelts, occupants are protected during 35-mph crashes
into a concrete barrier. But at 180 mph, both the car and the
driver have more than 25 times more energy. All of this energy
has to be absorbed in order to bring the car to a stop. This
is an incredible challenge, but the cars usually handle it
surprisingly well. In this edition of HowStuffWorks,
you will learn how NASCAR drivers are able to walk away from
so many crashes, and about the new safety devices being
developed to prevent future race-related fatalities.
The Car A NASCAR racing
car is basically a skeleton of strong metal tubing covered
with thin, metal sheeting. The cars are equipped with a
variety of safety devices that have evolved over the years in
response to accidents and crashes that have injured or killed
drivers. Let's start with how the car protects the driver.
The Roll Cage
One part of a NASCAR
car engine that was implemented for safety reasons is
now being pointed at as the cause for many of the
multi-car accidents during races. Restrictor
plates are used at NASCAR's super-speedways,
including Daytona and Talladega, to slow cars down.
The key to surviving a
crash is for the car to remove the energy from the driver's
body as slowly as possible. Street cars have many safety
devices designed with this in mind. The structure of a street
car is designed to crush and thus absorb a lot of energy,
giving the other safety devices, like seat belts and airbags,
more time to slow the driver's body down.
A NASCAR race car uses some of the same techniques. There
are three parts to the frame:
Middle section (including the roll cage)
The front and rear clip are built from thinner steel
tubing so that they will crush when the car hits another car
or a wall. The middle section is designed to be strong enough
to maintain its integrity during a crash, thereby protecting
In addition to being collapsible, the front clip is
designed to push the engine out of the bottom of the car --
rather than into the driver's compartment -- during an
The Seat The seat has
several important jobs:
It must keep the driver inside the roll cage of his car.
It must keep the driver from contacting anything hard
during a crash.
It must absorb some of the energy of the crash by
In the past, several deaths occurred when drivers still in
their seats were thrown from cars. To counter this, NASCAR
rules now require that the seat be attached, at several
points, directly to the tubular structure that forms the roll
cage, which is sometimes the only part of the car left intact
after a crash.
The shape of the seat is important, too. Most of the
seats found in NASCAR race cars wrap around the driver's rib
cage. This provides some support during a crash, spreading the
load out over the entire rib cage instead of letting it
concentrate in a smaller point. Some newer seats wrap around
the driver's shoulders as well, which provides better support
because the shoulders are more durable than the rib cage.
The seat in a NASCAR race car: Note how it
wraps tightly around the driver's ribs and
Restraints The safety
belts and the seat transfer most of the driver's energy to
the car during a crash. On a street car, the seatbelts are
designed to stretch during a crash, which limits the force
placed on the driver and gives him or her a little more time
to slow down. On a NASCAR vehicle, however, the seat belts are
much stronger -- they are designed to hold the driver tightly
in his seat so that his body slows down with the car.
The restraint used on NASCAR race cars is a five-point
harness. Two straps come down over the driver's shoulders,
two straps wrap around his waist and one comes up between his
legs. The straps are made from thick, padded nylon webbing.
They are much stronger than the seatbelts in a street car.
Recently, several deaths have occurred as a result of
severe head and neck trauma. Hoping to prevent those types of
injuries, NASCAR will be requiring the use of an approved
head-and-neck restraint. In October 2001, NASCAR
officials mandated the use of head-and-neck-restraint systems
for all drivers racing in the Winston Cup Series, Nascar Busch
Series or Nascar Craftsman Truck Series.
Window Nets The window
openings on the cars are covered by a mesh made from
nylon webbing. This webbing helps keep the driver's arms from
flailing out of the car during a crash. The G-forces
are so high during a crash -- between 50 and 100 times the
force of gravity -- that it is impossible for the driver to
control the position of his arms. This can be especially
dangerous if the car rolls over and starts tumbling.
The net covering the driver's window is
designed to keep debris out, and the driver's limbs in,
The net also has a quick release so that the driver
can get it out of the way without much effort.
Roof Flaps In 1994,
NASCAR introduced roof flaps -- a safety device
designed to keep cars from going airborne and tumbling over
the track. Before this, when the cars spun out at high speeds
(more than 195 mph / 324 kph), they would often fly into the
air once they had rotated about 140 degrees. At this angle,
the car takes on a shape that interacts with the wind very
much like a wing.
When the car has spun around 140 degrees, its
shape is very similar to that of a
If the speed of the car is high enough, it will generate
enough lift to pick up the car. To prevent this, NASCAR
officials developed a set of flaps that are recessed into
pockets on the roof of the car. Through wind-tunnel
testing, NASCAR determined that the area of lowest pressure is
at the back of the roof, near the rear window.
When the car reaches an angle at which it generates
significant lift, the low pressure above the flaps
sucks them open. The first flap to open is the one oriented at
a 140-degree angle from the centerline of the car. Once this
flap opens, it disrupts the airflow over the roof, killing all
of the lift. An area of high pressure forms in front of
the flap. This high-pressure air blows through a tube that
connects to the pocket holding the second flap, causing the
second flap to deploy. The second flap, which is oriented at
180 degrees, makes sure that the car continues to kill the
lift as it rotates. After the car has spun around once, it has
usually slowed to the point that it no longer produces lift.
The roof flaps keep the cars on the ground as they spin.
This allows the skidding tires to
scrub off some of the speed, hopefully allowing the driver to
regain control. If not, at least the speed is reduced before
The Windshield The
windshields on NASCAR race cars are made of Lexan,
which is the same polycarbonate material used on fighter-plane
canopies. This material is very strong, but also surprisingly
soft. This softness is actually what gives it its strength.
When an object hits the Lexan windshield, it doesn't shatter
it. Instead, the object scratches, dents or imbeds itself in
NASCAR race-car windshields are made out of
Lexan, the same polycarbonate material used to make
The windshields are usually constructed from three
relatively flat pieces of Lexan. Each piece is supported by a
framework built into the roll cage -- this gives the
windshield the strength to resist large objects. The downside
of a Lexan windshield is that it scratches very easily
-- you could scratch one with your fingernail. A bare Lexan
windshield would have to be replaced after every race because
of scratches from sand and other grit on the track. But
instead of replacing them, the NASCAR teams apply an
adhesive film to the windshields that is harder than
the Lexan and as clear as glass. After each race, the film can
be peeled off and replaced, leaving the Lexan unscratched.
Some teams apply several layers of this film and remove them
one at a time during the race.
Fuel Tanks In the 1950s,
NASCAR race cars used the fuel tanks from whatever street car
they were based on. There were some schemes for wood
reinforcements, but leaks and fires were common. Today's
22-gallon fuel tanks, also called fuel cells, have
built-in safety features to limit the chance of them rupturing
Fuel cells have a steel outer layer and a hard, plastic
inner layer. The fuel cell is located in the rear of the car
and is held in place by four braces that keep it from flying
loose during an accident. It is filled with foam, which
reduces the slosh of the fuel and any chance of explosion by
reducing the amount of air in the cell. If the cell does
ignite internally, the foam absorbs the explosion. The car
also has check valves that will shut off fuel if the
engine is separated from the car.
Restrictor Plates One part of a NASCAR car
engine that was implemented for safety reasons is now being
pointed at as the cause for many of the multi-car accidents
during races. Restrictor plates are used at NASCAR's
super-speedways, including Daytona and Talladega, to slow cars
down. The New Hampshire International Speedway was recently
added to that short list of restrictor-plate tracks following
the deaths of Adam Petty and Kenny Irwin on that
track within months of each other.
A restrictor plate is a square aluminum plate that has four
holes drilled into it. Hole size is determined by NASCAR and
varies between 0.875 inches and 1 inch (2.2 to 2.5 cm).
Restrictor plates are placed between the carburetor
and the intake
manifold to reduce the flow of air and fuel into the
engine's combustion chamber, thus reducing horsepower and
Restrictor plates were implemented in 1988 following
Bobby Allison's crash into a retaining fence at 210 mph
(338 kph), which endangered hundreds of fans. Also in 1987,
Bill Elliott set the track record by running a lap around the
track at 213 mph (343 kph). Some believe that if restrictor
plates weren't used, NASCAR cars could race on super-speedways
at speeds in excess of 225 mph (362 kph) due to the improved
aerodynamics of the cars over the past decade.
While NASCAR officials contend that restrictor plates are
needed to prevent high-speed crashes like Allison's, many
drivers complain that restrictor plates are the cause of
multi-car accidents. Restrictor plates reduce speed by about
10 mph, leaving the field of more than 40 cars bunched
tightly as they race around the track at 190 mph. If one of
these cars crashes, it usually causes several other cars to
crash along with it.
The Driver's Gear NASCAR lacks many of the
safety measures found in other racing series, including some
type of safety committee, a medical or safety
director or a consistent traveling safety team that
attends every race. A heavy burden is placed on the NASCAR
drivers themselves to make sure that they are as safe as
possible when they step inside their cars.
Even under normal, street-driving conditions, there is a
great chance that an accident will occur, and that numerous
injuries will result. In stock-car racing, the chances for
serious injury increase because the force at which these cars
collide with other cars or walls is far greater. NASCAR race
cars move faster and are heavier than conventional vehicles.
Before beginning a race, a NASCAR driver dons several
pieces of protective equipment that could save his life if an
accident were to occur. This gear covers the driver from head
to toe and would even protect him if a fire were to break out
in his car.
Helmet The head is
probably the most vulnerable part of the human body
during an accident. While the driver's body is strapped in
very tightly, the head can jerk around uncontrollably. The
helmet is designed to dissipate impact energy over the
entire helmet and prevent debris from puncturing it.
Every NASCAR driver is required to wear some type of
helmet. Most wear a full-face helmet, which covers the
entire head and wraps around the mouth and chin. Others wear
an open-face helmet, which only covers the head.
Drivers who wear the open-face helmet usually wear protective
goggles. They claim that a full-face helmet restricts their
shell design has been approved, a custom-made nickel model is
created for that particular helmet. Construction of the
outer shell begins with a thin layer of gelcoat. Then a
special resin, consisting of several types of glass, carbon,
Kevlar and other exotic fibers and weaves, is added to
the shell. This all combines to make the hard, glossy outer
Just underneath the outer shell is the BeadALL
liner, which is a special foam layer in the crown of the
helmet. The purpose of this liner is to absorb the energy that
the outer shell has not absorbed. This layer is made of
polystyrene or polypropylene.
The inner liner of most helmets is a form-fitting layer
that is made of either nylon or Nomex. Nomex is a
special fire-retardant material made by DuPont.
It doesn't melt, drip, burn or support combustion. Helmets are
also equipped with cheek pads, chin straps and visors. The
visor is made of a tough Lexan plastic. Lexan, which is
also used in NASCAR windshields, is commonly known for its use
All helmets go through some sort of testing before they are
considered safe enough for high-speed racing. Snell
Memorial Foundation is an independent organization that
sets voluntary standards for auto-racing helmets. To test the
impact resistance of a racing helmet, Snell places the
helmet onto a metal head form and drops it onto various types
of anvils. If the peak acceleration impacting the metal head
exceeds a magnitude of force equal to 300 Gs, or 300 times the
force of gravity, it is rejected. This level of impact is hard
to conceptualize -- a head-on impact at 30 mph (48 kph) into a
concrete wall is measured at 80 Gs. Most impacts on a race
track are between 50 and 100 Gs. A 100-G impact for a
160-pound (72-kg) man would feel like 16,000 pounds (7,257 kg)
pressing on top of him.
Suits Perhaps the most recognizable piece of NASCAR
racing gear is the driver's suit, which is emblazoned with
patches of the team's sponsors. These suits are almost as
recognizable as the drivers themselves. While most of us think
of this suit as a walking billboard, it is actually quite
important for the safety of the driver.
Photo courtesy Action
Sports Photography/Bill Davis Racing The drivers' trademark racing-suits protect
them in case of
The suit is made out of either Proban or the same
Nomex material that lines the inside of the driver's
helmet. As mentioned before, Nomex is a fire-retardant
material that protects the driver and crew if there is a flash
fire in the pits or a fire resulting from a crash. Unlike
other flame-retardant materials, the flame resistance of Nomex
cannot be washed out or worn away.
The Nomex is woven into a material that is used to make the
suit, gloves, socks and shoes worn by the driver. One of the
most common injuries in NASCAR is the driver's feet being
burned by the heat coming from the engine. These suits are
given a rating to determine how long they will protect
drivers from second-degree burns in a gasoline fire, which can
burn at between 1,800 and 2,100 degrees Fahrenheit (982 to
1,148 degrees Celsius). Ratings are provided by the SFI
Foundation, a non-profit organization that sets standards
for various pieces of racing equipment. SFI ratings range
between 3-2A/1 (three seconds of protection) to 3-2A/20 (40
seconds of protection).
Another piece of driver-safety equipment is called the
HANS device. This one is still being debated. In the
next section, you'll learn what a HANS device is and what the
controversy is about.
The HANS Device Four NASCAR drivers have
been killed on the track since May 2000 -- Adam Petty,
Kenny Irwin, Tony Roper and Dale Earnhardt
Sr.. All of these drivers were killed when their vehicles
slammed head-on into a retaining wall, causing a fracture to
the base of the skull. Some believe this type of injury is due
to the driver's head being left unsecured in the car while his
body is strapped securely to his seat.
The risk of severe injury, and possibly death, prompted six
NASCAR drivers to try out a new device called the Head
And Neck Support (HANS) system at the 2001 Daytona 500.
This device was co-developed by Dr. Robert Hubbard, a
professor of engineering at Michigan State University, and his
brother-in-law, former IMSA car driver Jim Downing. The HANS
device is designed to reduce the chance of injury caused by
unrestrained movement of the head during crashes.
The HANS device is a semi-hard collar made of carbon fiber
and Kevlar, and it is held onto the upper body by a
harness worn by the driver. Two flexible tethers
on the collar are attached to the helmet to prevent the head
from snapping forward or to the side during a wreck. The
device weighs approximately 1.5 pounds (0.68 kg).
Doctors have said that it is unclear if the HANS device
could have saved Earnhardt, but it is believed that the device
saved the life of a Championship Auto Racing Teams (CART)
driver in January 2001. While practicing for an upcoming race,
Bruno Junqueira spun out of control and slammed into a
concrete wall at 200 mph (322 kph). Junqueira, who was wearing
the HANS device, walked away from the crash without injury.
NASCAR officials have said that NASCAR race cars are
different from CART cars, and they are unsure if the device
would be as effective for NASCAR drivers. Drivers, including
Earnhardt, have complained that the device is too bulky, would
restrict movements and would make it difficult for drivers to
exit the car in emergencies. Hubbard/Downing Inc. said
it was producing only three to four of these helmets per day
just weeks before the 2001 Daytona 500, but received nearly
three-dozen orders within hours after Earnhardt's crash. Ford
has offered to pay for a HANS device for any driver who wants
to wear one.
In October 2001, NASCAR officials mandated the use of an
approved head-and-neck-restraint system for all drivers racing
in the Winston Cup Series, Nascar Busch Series or Nascar
Craftsman Truck Series.
The Track NASCAR races at about two-dozen
tracks every year, and no two tracks are the same. There are
ovals, tri-ovals, quad-ovals and road courses. There are short
tracks, speedways and super speedways that range from 0.5 to
2.5 miles long. No track is the same, but most of them have
one thing in common -- concrete retaining walls.
Photo courtesy Martinsville
Speedway in Martinsville, VA, has been a part of the
NASCAR circuit for more than 50
The concrete walls are in place to contain a car that rides
out of control. However, as we've seen, concrete walls don't
absorb any energy, making any crash into one potentially
deadly. Most NASCAR drivers who have died on the race track
have died from crashing into the wall. One solution being
proposed to make tracks safer is energy-absorbing
walls, or "soft walls."
Types of Soft
Walls Soft walls are typically built of some
kind of crushable material that can absorb the impact of a car
at high speeds, dissipating the force of the crash throughout
the material. Widespread implementation of soft walls on
NASCAR tracks is probably still several years away. However,
at least one track has already replaced small portions of
concrete walls with soft walls. Here's a look at a few of the
soft walls in use and in development:
Cellofoam - This is an encapsulated polystyrene
barrier -- a block of plastic foam encased in polyethelene.
Lowes Motor Speedway, a NASCAR race track, has
already installed small segments of Cellofoam on the inside
retaining wall of turns two and four.
Polyethylene Energy Dissipation System (PEDS) -
The Indy Racing League (IRL) has been funding the
PEDS system, which uses small polyethylene cylinders
inserted inside larger ones. Designers of PEDS believe the
system increases the wall's ability to withstand crashes of
heavy race cars. Indianapolis Motor Speedway has
already installed a PEDS on the fourth turn of its track.
Impact Protection System (IPS) -
Eurointernational has developed a soft wall made out
of layered PVC material placed on a honeycomb structure.
This inner piece of the wall is then wrapped in a rubber
casing. The barrier walls come in segments that are 5 feet 9
inches (1.8 meters) long and weigh 475 pounds (215 kg).
Holes are drilled in the concrete wall and cables are used
to tie the segments to it. Click here
for more information about the IPS.
Compression barriers - Another soft-wall idea has
been proposed by John Fitch, a Connecticut highway-safety
expert. His idea is to place cushioning materials, such as
tires, against the concrete wall, and then cover those
cushions with a smooth surface that would give when
impacted, and then pop back out to its previous shape once
the impact is over.
According to NASCAR Chief
Operating Officer Mike Helton, NASCAR has been researching
soft-wall designs for three to four years, but hasn't found
one suitable for its race tracks. Most of the designs they
have tested have some prohibitive flaws. Some of the walls are
made of material that breaks up, scattering across the track
and delaying the race. Earnhardt, one of the biggest critics
of new safety devices, once said that waiting for a splintered
soft-wall to be cleaned up would be worth it if it saved
Another criticism of soft walls is that a car can bounce
off a soft wall and back into oncoming traffic, posing a
danger to a greater number of drivers. Also, in NASCAR races,
cars often scrape against the outside wall. Some believe that
a soft-wall material would grab a car scraping the wall and
cause it to suddenly stop. Another possibility is that a car
crashing into a soft wall could get caught in the material,
and that quick stop could concentrate the energy of the crash
and cause even more damage.
Banking Track safety is
also affected by the degree of the track's banking, the
steepness built into the track. Tracks with a steep banking
allow cars to go faster, especially around the corners, which
is where a lot of the fatal accidents have occurred. If a
track's banking were 90 degrees, then the track would be
perpendicular to the ground. Obviously, no tracks are banked
at a perpendicular angle.
There is no set standard for the degree of banking designed
into a NASCAR track. Banking on NASCAR tracks range from 36
degrees in the corners to just a slight degree of banking in
the straighter portions. Of course, road courses have no
banking. Some believe that reducing the banking in the corners
of oval tracks could prevent a lot of the fatal wrecks that
we've seen recently.
Car racing is a dangerous sport -- possibly the most
dangerous sport. In NASCAR, drivers are racing cars that weigh
more than 3,000 pounds, speeding around a track at about 200
mph. Adding to the danger is the fact that cars usually race
in tightly packed groups, and sometimes race three cars across
on tracks that are only 50 feet (15 m) wide. Under such
conditions, there are going to be accidents, and crashes. The
purpose of the safety equipment is to minimize the harm caused
when one of these cars veers out of control.
For more information on NASCAR safety and related topics,
check out the links on the next page.