lane assist AUDI A7 2012 Owners Manual

2 Table of content s
Vehicle lite ratu re .. .. .. .. .. ... .
5
About thi s Owner' s Manual . . . 6
C ontr ols and equi pm ent .. ... .
Ins truments and controls .. . .
General illustration ...... ... .. ... .
Instruments and warning /
indicator lights ........ .. .. .. . .
Instruments ............ ... .. ... .
Warning/indicator lights .. ... ... .. .
Driver information display .... .. ... .
On-Board Diagnostic system (OBD) . . .
Opening and closing .. .. .... . .
Keys .. ...... ........... .. .. ... .
Power locking system ..... .. .. .. . .
Rear lid .. .. ........ ........ .... .
Child safety lock for the rear doors .. .
Power windows ............... .. .
Valet park ing . ........... .. .. ... .
Sliding/tilting sun roof ... .. .. .. .. . .
Clear vi sion ................... .
Lights . .. .. .. . .......... .. .. .. . .
I nter ior lights ............ .. .. .. . .
V1s 1on .......... ......... ... ... .
Wiper and washer system ... .... .. .
Mirrors .... .............. ... ... .
Seats and storage ...... ... ... .
General recommendations ... .... . .
Front seats ... ........... .. .. ... .
Head restraints .............. ... .
Seat memory . ........... .... ... .
Ashtray .. .. ... .... ...... .. .. .. . .
C igarette lighter .............. .. . .
12-vo lt sockets ............ ... .. . .
Sto rage ................. .. .. ... .
Roof rack ............... .. .. .. . .
L uggage compartment ... ... ... .. .
Pass-through with ski sack ... .. ... .
Warm and cold ............ ... .
C limate controls ......... ... .. ... .
Three-zone climate control ... .. ... .
8
8
8
10
10
11
22
27
29
29
31
35
37
38
39
39
41
41
44
45
45
47
so
so
51
52
53
54
54
55
55
57
59
62
64
64
65 Four
-zone automatic climate control .
Steering wheel heating ...... ... .. .
On the road ... ... ....... ... .. .
Steering . ..... .. ... ....... ..... .
Starting and stopping the engine .. . .
E lectromechanical parking brake . .. . 67
69
70
70
71
74
Speed warning system . . . . . . . . . . . . . 76
Cru ise control . . . . . . . . . . . . . . . . . . . . 77
Adaptive crui se control and
braking guard . . . . . . . . . . . . . . . . .
79
Introduction . . . . . . . . . . . . . . . . . . . . . 79
General information . . . . . . . . . . . . . . 79
Adaptive cruise control . . . . . . . . . . . . 81
Audi braking gua rd . . . . . . . . . . . . . . . 85
Messages . . . . . . . . . . . . . . . . . . . . . . . 86
Audi side assist . . . . . . . . . . . . . . . 88
Lane Change Assistant. . . . . . . . . . . . . 88
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Audi drive select . . . . . . . . . . . . . . 96
Driv ing set tings . . . . . . . . . . . . . . . . . . 96
Night vision a ssistant . . . . . . . . . 98
N ight vision assistant with detec ted
pedestrian marking . . . . . . . . . . . . . . . 98
Automatic Transmission . . . . . . 102
t. t
. ® 1p ronic ..... .. ... .. ..... ... .. . 102
Parking system . . . . . . . . . . . . . . . . 108
Genera l informa tion . . . . . . . . . . . . . . 108
Audi parking system p lus . . . . . . . . . . 108
Audi parking system plus with rear
view camera . . . . . . . . . . . . . . . . . . . . . 109
Adjusting the d isplay and warn ing
tones. .... .... .. ............. ... 113
Error messages 114
Homelink® . . . . . . . . . . . . . . . . . . . . 115
Universal remote control. .......... 115
Safet y first . . . . . . . . . . . . . . . . . . . . 118
Driving Safely . . . . . . . . . . . . . . . . . 118
General notes . . . . . . . . . . . . . . . . . . . . 118
Proper occupant seating positions . . . 119

Adaptive cruis e control an d bra kin g guard 79
Adaptive cruise control
and braking guard
Introduction
App lies to vehicles: with adaptive cruise co ntrol
The adaptive cruise control system assists the
driver by regulating vehicle speed and helping
to maintain a set distance to the vehicle
ahead, within the limits of the system. If the
system detects a moving veh icle up ahead,
adaptive cruise control can brake and then ac ­
celerate your vehicle . T his helps to make dr iv­
ing more comfortable both on long highway
stretches and in stop-and-go traffic.
Aud i brak ing guard can warn you about an im­
pending col lision w ith a vehicle up a head that
is slower or has s lowed down and start slow­
ing your vehicle down with the brakes
¢page 85.
Adaptive cruise control and Audi brak ing
guard have technica l limitations that you
must know, so p lease read this sect ion care­
fu lly, understand how the system works and
use them properly at all times.
General information
General information
Ap plies to vehicles: with adaptive cruise co ntrol
Fig. 81 Fr ont of th e ve hicle : sensors an d video camera
The areas that contain the radar and ultrason­
ic sensors and the video camera
¢ fig. 81
must never be covered by stickers, or other
things or coated with dirt, insects, snow or ice
that will interfe re with the adapt ive cru ise
control system and Audi braking guard . Re­
move snow with a hand brush and remove ice with a de-icing spray that does not contain
solvents.
T
he function of the Adaptive cruise cont ro l
system and A udi braking guard is limited un­
der some conditions.
- Objects can on ly be detected when they are
w ith in sensor range
¢page 81, fig. 84 .
-The system has a limited ability to detect
objects that are a shor t distance ahead,
off
to the side of your vehicle or moving into
your lane from the front or moves into your
lane from the side .
-When driving through curves
¢ page 80.
- Some kinds of veh icles are hard to detect;
for examp le motorcycles, veh icles with high
ground clearance or overhanging loads may
be detected when it is too late or they may
not be detected at a ll.
- Stationa ry objects
c::> page 80.
A WARNING
Improper use of the adaptive cruise con­
trol can cause collisions, other accidents
and serious personal injury.
- Never let the comfort and convenience
that adaptive cruise control and Audi brak ing guard offer distract you from the
need to be alert to traffic conditions and
the need to remain in full control of your
veh icle at a ll t imes,
- Always remember that the adaptive
cru ise cont rol and Aud i brak ing guard
have lim its -they will not s low the vehi­
cle down or maintain the set d istance
when yo u drive towards an obstacle or
someth ing on or near the road tha t is not
mov ing, such as vehicles stopped in a
traffic jam, a stalled or disabled vehicle.
If registered by the radar sensors, vehi­
cles or obstacles that are not moving can
trigger a collision warning and if con­
f irmed by the video camera, an acute col­
lision warning.
- Always remember that the adaptive
cru ise contro l cannot detect a vehicle
that is driving towards you in your traffic
-
lane and that it cannot detect narrow ..,.

Adaptive cruise control and braking guard 85
@ Tips
- Distance 3
is set automatically each time
you switch the ignition on.
- Your standard settings are automatically
stored and assigned to the remote con­
trol key being used.
Audi braking guard
Descript ion
Applies to vehicles: with adaptive cruise contro l
Fig. 90 Instrument cluster: approach warning
Audi braking guard uses radar sensors and a
video camera. It is active at speeds above
about 6.2 mph (10 km/h) and also works
within system limits when adaptive c ruise
control is switched off.
On vehicles w ith adaptive cru ise control and
Audi side assist (Aud i pre sense plus), system
functions also engage when a collision is im­
minent
c::> page 182.
What can Audi braking guard do?
When detected in time, the system can assess
situations when a vehicle ahead brakes sud­
denly or if your own veh icle is traveling at a
h igh speed and approaching a veh icle up
ahead that is moving more slowly . Audi brak­
in g guard does not react if it cannot detect
the situation.
The system advises you of various s ituations:
- The
distance warning is given if you are too
close to the vehicle ahead for a long time. If
the vehicle ahead brakes sharply, you will not be able to avoid a coll is ion . The ind icator
light
I in the disp lay comes on. Take imme- diate action to avoid
the collision and in­
crease the distance to the vehicle up ahead.
- The
approach warning is given when a de­
tected vehicle up ahead in your lane is mov­
ing much more slowly that you are or if it
brakes sharp ly. When this warning is given,
it may only be possible to avoid a collision
by swerving or braking sharply. The indicator
light
I and the symbol in the display will
warn you about the danger
c::> fig . 90 . You
w il l also hear an acoustic signal.
If you do not react fast enough or do not react
at all to the situation, Audi braking guard w ill
intervene by braking and the message
braking
guard intervention
will appear.
- If a collision is imminent, the system will
first provide an
acute warning by braking
sharply.
- If you do not react to the acute warning, Au­
di braking guard will brake w ith increased
force in severa l stages to reduce the speed
in a poss ible collis ion. On veh icles with
adaptive cruise control and Audi side assist
(Audi pre sense plus), the system can brake
with increasing force up to maximum dece l­
eration shortly before a sensed collision
c::>page 182.
-If the Audi braking guard senses that you
are not brak ing hard enough when a colli­
sion is imminent, it can increase the braking
force.
Audi braking guard takes the driver's reaction
time into consideration in order to provide
timely warnings. The system reaction time de­
creases automatically in some situations, for
example when it detects acce lerator pedal use
or steering input . The Audi braking guard in­
tervent ion stops in certa in situations, for ex­
amp le if you press the accelerato r pedal to
pass the vehicle moving ahead of you in your
lane .
Which functions can be controlled?
You can switch Audi braking guard and the
distance/approach warning on or
off i n the
MM I ¢ page 86, Settings in the MMI.

88 Audi side a ssist
Audi side assist
Lane Change Assistant
Description
App lies to vehicles: wit h side ass ist
The side assist helps you when changing
lanes.
F ig . 91 Rear bumper : Pos it ion of rada r se nsors (not
v is ib le on outs ide)
:R 0 0 C)
" a,
F ig . 92 S ignal lig ht on the outside m irror -driver's side
Side assist uses radar sensors (not visib le on
outside)¢
fig. 91 to help the driver check
blind spots, and see what is happen ing in traf­
f ic beh ind the vehicle¢
page 89, fig. 93.
Signa l lights are built into both o utside mir­
rors ¢
fig. 92. The s ignal light on the left out­
side mirror assists when moving over into the
left lane and the signal light on the right out­
side mirror assists when moving over into the right lane.
The s ignal light comes on to tell you that side
assist has detected a vehicle on that side and
that the position of this othe r vehicle should
be taken into account if yo u were to change
l anes . This is called the
informati ona l stag e
s ignal ¢
page 90. The informational stage
signal is designed so that you notice it only
when you are look ing in the ou ts ide mirror. When you activate the turn signal and side as­
sist detects a vehicle in a notable location, the
corresponding signal on the outside mirror
¢ fig. 92 (!) flashes br iefly and brightly sever­
al times. This is the
alert stage signal
¢ page 90.
Activating and deactivating
Appl ies to veh ic les : w it h side assist
Activating
• Press th e button @¢ page 88 , fig . 92 . The
ind icator on the button lights up .
Deactivating
• Press the button again. The indicator light
on the button goes out.
T he system works at speeds faster than
19 mp h (30 km/h).
A WARNING
-
-Improper reliance on the side assist sys-
tem can cause collis ions and serious per­
sonal injury:
- Never rely on ly on s ide ass ist whe n
changing lanes.
- Always chec k rear v iew mirro rs to make
su re that it is sa fe to change l anes.
- Side assist cannot de te ct all veh icles un­
der a ll condi tions- d anger of a cc iden t!
- Side assist cannot detect vehicles in time
to a le rt you when they ap proa ch from
be hind at very hig h spee d, or fall drop
back very q uickly.
- The radar sensor's
vision ca n be reduced
or entire ly blocked by rain, snow, and
heavy spray . This can resu lt in side assist
not adequately detecting vehicles or, in
some cases, not detecting them at all.
Always keep an eye on the direction you are traveling and the relevant area
around the vehicle .
- Please note that side ass ist indicates
there are approaching vehicles, or vehi­
cles in your blind spot, o nly after you r ve­
h icle has reach ed a driv ing speed of at
least 19 mph (30 km/h). ..,

-Side assist signal does not work around
tight corners (turning radius less than
328 feet or 100 m).
- Side assist is no replacement for the driv­
er's full attention. The driver alone is re­
sponsible for lane changes and similar
driving maneuvers. Always keep an eye on the direction you are traveling and the
relevant area around the vehicle.
(D Note
- To ensure that you do not adversely af­
fect side assist, do not block the area on
the rear bumper where the radar sensors
are located with foreign objects (such as
stickers or bicycle racks).
- Make sure that the signal light on the
outside mirror is not blocked by stickers
or other items.
(D Tips
- Side assist automatically deactivates if it
detects that the radar sensors are
blocked¢
page 94. The indicator light
on the button goes out.
- The area on the bumper where the radar
sensors are located must consistently re­
main free of snow, ice, and heavy soiling
so that side assist can function properly.
Follow the additional notes on
¢ page 94.
- Additional tinting on the front side win­
dows can make it harder to see and cor­
rectly understand the signal light on the
outside mirror.
- For Declaration of Compliance to United
States FCC and Industry Canada regula­
tions
Q page 2 76.
Audi side assist 89
Sensor detection area
Applies to vehicles: with side assist
Fig. 93 Schematic illustrat ion : Sensor detection a rea
The detection ¢ fig. 93 of the radar sensor de­
tection area is made up of:
- the approach area (light red area)
(D, about
230 feet (70 m) behind the vehicle, and
- the "blind spot" (dark red area) @.
Th e radar sensors cover the adjacent left and
r ight lanes. Other lanes are
not covered by the
radar sensors.
(D Tips
Side assist does not measure actual lane
width. The system assumes a fixed lane
width. Detection in the left and right lanes
is based on this assumed lane width.
When driving on narrow roads or when
driving to the left or right of the center of
a travel lane, it is possible that vehicles
will be detected that are
not in the lane
next to the lane you are using
~page 93.
Operation
Applies to vehicles: with side assist
Side assist compares the distance and differ­
ence in speed of detected vehicles with the
speed of your vehicle. Whenever the differ­
ence in speed and distance is registered as no­
table if you were to change lanes, a signal
light appears on the respective mirror.
The signal can light up if you are passed by a
vehicle or if you are passing another vehicle.
If you pass another vehicle slowly (difference
in speed less than 9 mph, or 15 km/h), the ..,.

90 Audi side assist
signal light will come on as soon as the other
vehicle is in your blind spot and is detected by
side assist. When the difference in speed is
greater, the signa l light will not come on.
Informational and alert stage signals
Applies to vehicles: with side assist
Side assist has two s ignal stages:
- the informational stage signal, and
- the a le rt stage signa l.
Side assist helps you by using the appropriate
signal stage, depending on whethe r or not
you have activated the turn signal, and thus
have indicated that you are or are not chang­
ing lanes.
Informational stage signal
As long as you have not activated the turn sig­
nal, side assist informs you of detec ted vehi ­
cles that are registered as being in a notable
l ocation if you were to change lanes. Whenev ­
er the detected vehicle's difference in speed
and distance is registered by side assist as no­
table, the signal light on the respective m irror
produces muted illumination.
The brightness of the informational stage sig­
na l is designed not to be as intense, so that it
does not interfere with your view of the road
when you are driving and have no intention of
changing lanes. When you look in the outside
mirror, you can clearly see the informat ional
stage signal.
Alert stage signal
When you activate the turn signal, and side
assist has detected a vehicle in a notable loca­
tion on that part icular side, the signal l ight on
this side mirror flashes bright ly . The repeated
brief and bright flashing of the alert stage
signal reminds you to carefully check traffic to
the rear in the outside mirror and over your
shoulder, so that yo u can safely complete the
lane change
c::> & in Safety tips on page 94.
(D Tips
The brightness of the signal light on the
outside m irrors can be adjusted with the
MMI c::> page 93.
Driving situation: Fast approaching
vehicles
Applies to vehicles: with side assist
©
@
Fig. 94 Side ass ist: Fast approach ing ve hicles
@ Signal on outside mirror does not light
up
No vehicle was detected by the sensors . The
signal on the o utside mirror does not light up
c::> & in Safety tips on page 94.
@ Informational stage signal lights up
A fast approaching vehicle - in the left-hand
lane for example - was detected by the sen­
sors . Although this vehicle is still far away, it
should be taken into account if yo u were to
change lanes, due to the considerab le differ­
ence in speed. The informational stage s ignal
on the outside mirror lights up
c::> page 90 . ..,.

@ Alert stage signal flashes
If you activate your turn signal in driving sit­
uation @, the signa l briefly f lashes repeated­
ly. Side assist is a lerting yo u to a vehicle that
you may not have noticed.
@ Tips
- The faster a vehicle approaches from the
rear, the sooner the signa l on the outside
mirror lights up. Side assist will signa l,
at the latest, when a detected vehicle en­
ters your "blind spot".
- When vehicles approach very quickly,
changing lanes can be dangerous even if
the signal on the outside mirror does not
light up.
Driving situation: Slowly approaching
vehicles
Appl ies to vehicles : wit h side ass ist
®
F ig . 95 S ide ass ist: S lowly approaching vehicles and ve·
h ides in your blind spot
@ Signal on outside mirror does not light
up
A vehicle approaching slowly -in the left-hand
lane for examp le -was detected by the sen­
sors. Because of the small difference in speed
and the considerab le distance from your vehi-
Audi side assist 91
cle, the signal on the outside mirror wi ll not
light up
~.& in Safety tips on page 94 .
@ Informational stage signal lights up
The distance between your ve hicle and that of
the slowly approaching vehicle has narrowed.
T he informational stage signal on the outside
mirror lights up.
As soon as the difference in speed and dis­
tance is registered as notable if you were to
change lanes, a signal on the m irror lights up.
Side assist will signal at the latest when a de­
tected vehicle enters your "blind spot".
@ Alert stage signal flashes
If you activate your turn signal in driving sit­
u ation @, the signal light briefly fla shes re­
peatedly. Side assist is alert ing you of a vehi­
cle that you may not have noticed.
(D Tips
- Th e faster a vehicle approaches from the
rear, the soone r the signal on the outside
mirror lights up. Side assist will signal,
at the latest, when a detected vehicle en­
ters your "blind spot".
- When vehicles approach very quickly,
changing lanes can be dangerous even if
the signal on the outside m irror does not
light up.

92 Audi side assist
Driving situation: Vehicles dropping
back slowly
Applies to vehicles: with side assist
i:i N 9 J:
-------::~
®
Fig. 96 Side ass ist: Veh icles d ropping back slow ly
CD Signal on outside mirror does not light
up
The vehicle that you passed has not yet been
detected by side assist . The signal on the out­
side mirror does not light up¢
A in Safety
tips on page 94.
@ Informational stage signal lights up
A vehicle dropping back slowly on the right
(difference in speed of less than 9 mph, or 15
km/h) has been detected by side assist. The
informational stage signal on the outside mir ­
ror lights up.
@ Alert stage signal flashes
If you activate your turn signal in driving sit­
uation@, the signal briefly flashes repeated­
ly. Side assist is alerting you of a vehicle that
you may not have noticed .
Driving situation: Vehicles dropping
back quickly
Applies to vehicles: with side assist
®
Fig. 97 Side ass ist: Vehicles dropping ba ck quickly
CD Signal on outside mirror does not light
up
The vehicle just passed has not yet been de ­
tected by side assist. The signal on the out­
s ide mirror doe s not light up¢
A in Safety
tips on page 94 .
@Signal on outside mirror does not light
up
The vehicle dropping back quickly on the right
( d ifference in speed of more than 9 mph, or
15 km/h) has been detected by side assist ,
but is not considered notable in the event of a
lane change, because it is dropping back so
quick ly. The signal on the outs ide mirro r does
not light up¢
A in Safety tips on page 94.
@ Signal on outside mirror does not light
up
If you activate your turn signal in driving sit­
uation @, the signal still does not light up on
the outside mirror ¢
A in Safety tips on
page 94 .

MMI settings
Applies to vehicles: with side assist
The basic brightness setting of the signal on
the outside mirror can be adjusted via the
MMI.
~ Select : ICARI funct ion button> Car systems
control button > Driver assist > Audi side
assist.
The brightness of the signal light for both the informational and alert stages is automatical­
ly adjusted to ambient light conditions. In ad­
d ition, you can adjust the
basic brightness
separately, via the brightness function .
W hile making the adjustment, the new
brightness setting is displayed briefly . The
brightness displayed is that of the informa­
tional stage signal. The alert stage signal
brightness is linked to the informational stage
signal brightness.
The informational stage signa l br ightness
should be adjusted so that you not ice the sig­
nal illumi nation when you look in the outside
mirror, but not when you look forward
through the windshield .
I n very dark or light sur roundings, the auto­
mat ic brightness setting adjusts signal light
brightness to maximum or minimum intensi­
ty, as needed. In circumstances such as these,
you may not notice any change in the bright­
ness on the outside mirror when adjusting the
basic brightness. You may not notice the
change until lighting conditions are normal
again.
(D Tips
- Side assist is not active when the basic
brightness is adjusted. The signal light
comes on briefly to help you make the
adjustment .
- Your settings are automatically stored
and ass igned to the remote control key
being used.
Audi side assist 93
General information
Applies to vehicles: wit h side assist
Side assist has limits and cannot detect vehi­
cles unde r al l road and weather conditions.
Please remember system limitations and nev­
er rely on the system, especially when :
- driving through curves
c::> page 93,
-lanes are of diffe rent widths c::> page 93 .
When driving through curves
Applies to vehicles: wit h side assist
Side assist cannot detect ve hicles in curves
with a turning radius of less than 328 feet
(100 m).
When dr iving through a curve, it is poss ible
that side assist may reg ister a vehicle two
lanes over, and the signal on the outside mir­
ror will light up.
Lane width
Appl ies to vehicles: wit h side assist
Fig. 98 Lanes of a normal width are in detect ion area
Fig. 99 Narrow lanes: S ide assist may detec t vehicles
two lanes away
Side assist's detection area is designed to cov-
er lanes of standa rd width to the left and ..,.

94 Audi side assist
right of your travel lane, depending on wheth­
er you drive in the center of your lane or closer
to the edge.
If you drive in narrow lanes, s ide ass ist's de­
tection area may a lso include other lanes -es­
pecia lly if you tend to drive on the edge of
your lane¢
fig. 99. Under these condit ions,
vehicles can also be detected that are two lanes away, and side assist then could switch
between the informat ional and warning stage
signals .
When driving in very w ide lanes, vehicles in
the adjacent lane may not be detected be­
cause they are not inside the detection area .
Notes
Messages in instrument cluster display
Applies to vehicles: with side assis t
If side assist turns off automatically, the indi­
cator light on the button wi ll go out and you
will see a message in the instrument cluster
d isplay:
Audi side assist: not available. sensors
blocked
The side assist sensors are built into the rear
bumper on the left and right (not visible on
the outside)
¢ page 88, fig. 91 . To ensure that
you do not adversely affect the way side assist
functions, foreign objects (such as stickers or
b icycle racks) should not be attached to the
a rea on the rear bumper where the sensors
are located. If side assist functions are ad­
versely affected, you will see this message in
the instrument cluster display. Remove any ­
thing that may be blocking the sensors .
If no vehicle is detected for a longer period of
time while driving, side assist will also switc h
off a utomatica lly.
Audi side assist currently not available
If there is a temporary problem (such as the
ve hicle's battery charge being low), s ide ass ist
cannot be activated tempo rari ly.
Audi side assist: system fault
Have the system checked by an authorized Au­
di dealer or qualified workshop.
Audi side assist: not available when
towing
T he radar senso r's view is limited when tow­
ing a trai le r. For vehicles with a fa ctory instal ­
led towing hitch or a trailer hitch that was in­
stalled later according to factory specifica­
tions, side assist is automatically deactivated
as soon as the electrical connection to the
trailer's electrical socket is made, and this sta­
tus message appears in the instrument clus ­
ter display . Deactivation cannot be guaran­
teed when using a retrofitted towing hitch
that was
not installed according to factory
specifications.
Safety tips
Appl ies to vehicles : wi th side assist
The side assist detection may be limited when
driving aro und narrow street corners, on hilly
streets, and under poor weather cond itions.
It is possible that the radar sensors may also
detect other objects, such as high or stag­
gered guardrails .
Side assist does not measure actual lane
width. The system assumes a fixed lane width.
Detection in the left and right lanes is based
o n this ass umed lane width . When driving on
narrow roads or when driving to the left or
right of the center of a trave l lane, it is poss i­
ble that vehicles will be detected that are
not
in the lane next to the lane you are using.
A WARNING
- Improper reliance on the side assist sys­
tem can cause collis ion s and serious per­
sonal injury:
- Never rely only on side assist when
changing lanes .
- Always check rear view mirrors to make
sure that it is safe to change lanes.
- Side assist cannot detect all vehicles un-
der all conditions- danger of accident! ..,.