Cycling at Night
By Bruce Rosar and Steve Goodridge of the NCBC
For good reason, North Carolina state law requires bicycles operated
at night to be equipped with a headlamp in front and a red light or
red reflector in back. Never ride at night without a headlamp and a
bright rear reflector. Although most bicycles are sold with small "toy"
reflectors, these are terribly inadequate for safe night cycling. The
car-bike collision rate is several times higher at night than during
daylight, but the vast majority of these crashes involve cyclists operating
without proper nighttime equipment and can be easily prevented. Proper
equipment makes cyclists visible to motorists and can make cycling at
night much safer than statistics suggest that it is.
Being Visible and Predictable
Proper bicycle lighting is important for two reasons:
1. It makes you visible and predictable to other road users
2. It can help you see well enough to avoid hazards and navigate your
Many cyclists ride in urban environments where they feel that they can
see well enough to navigate, so they don't bother with headlamps. This
is terribly dangerous, because without a headlamp, motorists often do
not see them, even under street lamps. Reflectors provide good visibility
for overtaking traffic, but most dangers of car-bike collisions come
from the front or side of the cyclist. The headlamp beams of motor vehicles
on intersecting paths with cyclists often do not shine upon the reflectors
of a bicycle until it is too late for the motorist to yield right of
way or avoid collision. Figure 1 below shows the positions of two vehicles
that might be about to move across the cyclist's path. In neither case
are the vehicle headlamp beams shining on the cyclist's reflectors.
Only the active emission of light from a headlamp can make the cyclist
sufficiently visible in these situations.
Figure 1: Car headlamps often
do not illuminate the cyclist's reflectors, creating a danger at intersections.
A headlamp on the bicycle is much more visible to motorists in these
Bicycle headlamps should emit a steady white (or nearly white) light
because this indicates the direction that the vehicle is traveling.
Most vehicles, including aircraft and boats, exploit a color convention
to indicate orientation or direction of travel. For road vehicles, red
lights belong in back, orange lights on the side, and white lights in
front. The fact that reverse-gear lights of a motor vehicle are white
provides an important cue as to what the motorist is about to do. It's
important for cyclists to comply with this convention in order for other
road users to predict their actions. For instance, using a red lamp
on the front of a bicycle is likely to cause opposite-direction divers
to underestimate the closing speed between vehicles because they will
expect the red-lighted object to be either stationary or moving in the
A red rear lamp or reflector makes a bicycle visible to overtaking traffic.
It's important to make this reflector or lamp large enough and bright
enough to be seen by motorists at enough distance to slow or stop in
time when traveling at high speeds. Color is generally less important
on the rear of the vehicle, since overtaking motorists will not be any
less cautious when viewing another color, but red is a universally understood
warning indicator. A variety of red LED (Light Emitting Diode) tail
lamps available for bicycles; these lamps are visible at longer distances
and a wider angles than most reflectors, and don't depend on motorists'
headlights to be effective.
Note that side reflectors don't hurt, but they are rarely of much use
because if a car's headlamps are shining on them, you will either be
riding ahead and out of the way before the car arrives or it is already
too late for the motorist to avoid you.
Seeing What's Ahead
The amount of light your headlamp needs to shine on the roadway in order
to see your way depends on where and how fast you ride. A cyclist riding
at high speed on a dark rural road needs a long, relatively narrow beam
of light to see surface conditions and obstacles far enough ahead. A
mountain biker riding over challenging off-road terrain needs a wide,
bright beam to find suitable paths over obstacles and around turns.
By contrast, an urban cyclist operating under street lamps requires
just enough beam strength to allow navigation of the occasional dark
stretch at reduced speed.
The faster you ride, the longer your effective headlamp beam needs to
be; if you double your speed, you need to see twice as far. Note that
since the power of reflected light decreases in proportion to the square
of distance from the lamp, doubling the range for a given reflection
power requires four times as much light power from the lamp. For a typical
headlamp beam pattern, a motorist traveling at 60 mph needs a headlamp
of about 10,000 candlepower to see well; a cyclist operating at 15 mph
can see well enough with less than 600 candlepower (e.g. 12 watt halogen),
and a cyclist operating at 7.5 mph can see far enough in with less than
150 candlepower (e.g. 3 watt halogen). The light provided by a bicycle
headlamp may be focused into a narrow beam for maximum range, or may
be spread out for better peripheral vision. A three watt lamp can be
focused into a beam suitable for high speed cycling on the darkest roads,
but will not give much illumination of turns. Any headlamp, even the
cheapest clip-on battery kind, is much safer than none at all - you
just need to ride slower to compensate for reduced range.
On totally dark roads, our eyes adapt to the darkness and allow us to
see surprisingly well with a low-power headlamp. However, street lamps
and the headlamps of oncoming cars can inhibit or reverse the adaptation
of our eyes. This makes cycling on partially-lit roads or with oncoming
traffic on rural roads more challenging with low-power headlamps. It's
a good idea to use the most powerful headlamp available for your cycling
needs and your price range.
Special Hazards to See
Remember that motor vehicle traffic isn't the only hazard at night.
Don't be surprised to find animals, unlit pedestrians dressed in black,
and unlit wrong-way cyclists in your path at night. Look for them carefully,
and give them wide berth when you see them. Also remember that it's
harder to see potholes and gravel. Also, wet road surfaces do not reflect
as much light as dry roads, making driving lights (head and frame mounted
white lights) less effective.
Increased Hazards from Motorists
On average, the percentage of highway users who are impaired by fatigue,
poor night vision and alcohol increases at night. Drunk, drowsy, and
severely distracted drivers are the greatest threat to lawfully operating
cyclists at any time of day. Fortunately, the total number of motorists
on the roads usually decreases at night. Many experienced night cyclists
who use proper lighting report that overtaking motorists give them wider
berth after dark. With reduced traffic and strong lights, it is arguable
that the properly equipped night cyclist may actually be more visible
and easier for motorists to avoid than the daytime cyclist.
Avoid Riding into the Sun
One situation which cannot be helped by night equipment is poor cyclist
visibility when riding directly into sunrise or sunset. Motorists are
often blinded to the point that they can barely see more than the outlines
of motor vehicles ahead of them, yet they continue to drive at normal
speeds. If possible, simply wait for the sun to set (you have your lights,
right?) or to rise higher before riding; otherwise try to stay farther
right out of the normal traffic stream and keep in mind that motorists
approaching from behind may not see you.
Choosing the Right Equipment
A variety of bicycle headlamps are available depending on the user's
preference for range, light output, mounting style, and cost. Helmet
mounted lights put the light where you're looking. Bike mounted lights
put the light near where you bike is going to be very soon. For maximum
effectiveness, use both. Note that it's also good to have a back-up
light source or spare bulbs and batteries(and the tools to change them).
The cheapest, shortest-range lights suitable for emergencies or occasional
urban use are low-wattage clip-on lamps powered by batteries stored
inside the lamp housing. These lamps can get you home safely when you're
out after dark, and are good as a back-up, but they don't have enough
light output for high speed cycling on dark roads, they have limited
range, and they eat batteries.
Rechargeable battery-powered lighting systems provide the highest light
output, making them especially popular for mountain biking, and can
offer operating times of over two hours between charges. Some even have
fuel gauges and multiple power settings so you can control your range.
The high power availability allows wide beam width which also maximizes
visibility to motorists. Recent advances in battery and lamp technology
provide increased power efficiency, lower battery weight, and easier
charging, than previous battery-powered headlamp systems. However, these
lamp systems usually cost over $100. Examples of battery light manufacturers
include NiteRider and CatEye.
For unlimited range without the worry of battery maintenance, generators
are the ideal choice. Generators may be built into the front hub or
attach to the tire. Early-generation generators would not provide any
light with the bicycle stopped, would glow dimly at low speed, and could
potentially burn out the lamp at high speed. Many modern generator systems
use smart electronics to regulate power production such that the lamp
is bright even at slow cycling speeds, and ensure there is no danger
of burnout at high speeds. Some are even combined with rechargeable
batteries to provide illumination when stopped; the batteries recharge
while the cyclist is moving. Generator powered lights reduce your acceleration
ability somewhat because of the extra drag, which may be 10% of your
pedaling effort. Some generators, such as the Schmidt Dyno Hub, are
built into the front wheel hub. Bottle generators, such as the Dynosys
LightSpin, rub against the tire.
Front strobes or flashers may also add to the cyclist's conspicuity.
However, these should not be used as a substitute for a normal headlamp.
When conditions are right, reflectors can be as visible as rear lamps
- but conditions are not always right. Bicycle and automotive reflectors
use the cube-corner reflection principle to reflect light back along
the same path from which it came. This means that the observer's eye
must be very close to the light source - less than a two degree arc,
in fact - to see a strong reflection. If the driver's side headlamp
is not turned on or working, the reflector may not be visible to the
driver. The reflector must also be close to perpendicular to the observation
Most bicycles come with small reflectors required by the Consumer Products
Safety Commission. These reflectors are too small to provide adequate
visibility under many realistic road conditions. A typical CPSC reflector
provides only 1.7 square inches of directly exposed surface area and
1 square inch of surface angled to one side under optimum viewing conditions.
The cyclist is better off replacing this rear reflector with a larger
one from an automotive store. A 3" diameter round automotive reflector
provides 7 square inches of reflector area. An oblong "trailer"
reflector provides six square inches.
Note that an amber reflector is 2.5 times as bright as a red reflector
under the same headlight illumination. By law, a red reflector is required,
but adding an amber reflector to the red one isn't a bad idea. With
this combination, you'll be over ten times brighter than with just one
Reflectors are very sensitive to mounting location and orientation.
Reflectors on the frame should be mount low to reflect the lights of
other vehicles sooner. The face of the reflector should be perpendicular
to the ground. If the rear reflector is where it may be sprayed by mud
from the tire, clean it often.
Inexpensive tail lamps, typically employing red, energy-efficient light
emitting diodes (LEDs), don't rely on a motorist's headlamps to be visible,
and can be seen clearly from the side as well. These lamps will last
many hours on a pair of disposible batteries. However, they often glow
dimly long before they fail; it's important to inspect them before each
ride and change the batteries regularly, especially in cold weather.
Above all, use a reflector in addition to the tail lamp so you have
Some extra-bright tail lamps, such as the NiteRider Tail Lamp, run off
of the same rechargeable battery used for the headlamp. These are excellent
for long-range visibility and are even visible in daylight.
Solid versus Pulsating versus Flash
There is some controversy over whether pulsing tail lamps are better
than solid tail lamps. A rapid pulse is better than a slow flash, because
it is easier to track visually. (Remember the difficulty catching fireflies
between flashes?) The rapid pulse is also grabs attention more readily
at long distances than does a solid lamp. Proponents of solid lamps
say solid lamps are just as visible at short distances, which they say
is what counts, that solid lamps are less annoying or distracting, and
that there is little use in looking different from other traffic. Proponents
of flashing lamps believe that is useful to alert motorists to the presence
of a bicyclist farther ahead so the motorist can better prepare in advance
to overtake with caution.
General Conspicuity Tips
con·spi·cu·i·ty : The quality of being conspicuous;
con·spi·cu·i·ty equipment : Equipment to
make an object more noticeable.
Conduct a survey of your conspicuity in the dark. If you can, have a
friend ride with your clothing and equipment while you check out the
conspicuity under different lighting conditions.
To increase your conspicuity, display bright colors that contrast with
your surroundings. Fluorescent lime-green and lime-yellow are the best.
Red and orange are not as bright, and white can be problematic in visible
moisture (fog, snow, etc.).
Use retro-reflective materials on clothing and equipment. Consider adding
retro-reflective carriers, such as a vest and bands (wrists and ankles).
Stick-on retro-reflective material can be applied to spokes, helmets,
fenders, pedals, racks, shoes, panniers, etc. Redundancy and diversity
are both good attributes for conspicuity equipment.
The effectiviness of conspicuity devices suffers when dirty or worn.
Inspect and then clean, repair or replace conspicuity equipment as required.