Driver visibility

In transport, driver visibility is the maximum distance at which the driver of a vehicle can see and identify prominent objects around the vehicle.^[1] Visibility is primarily determined by weather conditions (see visibility) and by a vehicle's design.^[2] The parts of a vehicle that influence visibility include the windshield, the dashboard and the pillars. Good driver visibility is essential to safe road traffic.

Blind spots may occur in the front of the driver when the A-pillar (also called the windshield pillar), side-view mirror, and interior rear-view mirror block a driver's view of the road. Behind the driver, there are additional pillars, headrests, passengers, and cargo, that may reduce visibility. Blind spots are affected directed by vehicular speed, since they increase substantially the faster one goes.

A-pillar blind spot

Forward visibility

This diagram shows the blocked view in a horizontal-plane in front of the driver. The front-end blind spots caused by this can create problems in traffic situations, such as in roundabouts, intersections, and road crossings. Front-end blind spots are influenced by the following design criteria:

• Distance between the driver and the pillar
• Thickness of the pillar
• The angle of the pillar in a vertical plane side view
• The angle of the pillar in a vertical plane front view
• the form of the pillar straight or arc-form
• Angle of the windshield
• Height of the driver in relation to the dashboard
• Speed of the opposite car

40° angle A-pillar bar blind spots

Effects of A-pillar angle on visibility

Most passenger cars have a diagonal pillar as shown in this side view. The angle between the horizon and A-pillar is approximately 40 degrees with a straight pillar that is not too thick. This gives the car a strong, aerodynamic body with an adequately-sized front door.

vertical A-pillar having small blind spots

Panoramic windshield

The sides of a panoramic windshield are curved, which makes it possible to design vertical A-pillars that give the driver maximum forward visibility. However, it is impossible to design an aerodynamic small car with a vertical A-pillar because the more vertical the A-pillar is, the less space the door opening has, and the greater frontal area and coefficient of drag the vehicle will have.

Examples of cars with an almost vertical A-pillar:

• Honda Step Bus Concept
• Saab 900
• School bus
• Almost all Cadillacs from 1954–1959

A-pillar bars reduce driver visibility

Flat windshields

Some modern car designs have an extremely flat A-pillar angle with the horizon. For example, the Pontiac Firebird and Chevrolet Camaro from 1993-2002 had a windshield angle of 68° with the vertical, which equals just 22° with the horizon.^[3]

A flatter A-pillar's advantages include reducing the overall drag coefficient and making the car body stronger in a frontal collision, at the expense of reducing driver visibility in a 180° field of view from left to right.

Car with a "quarter glass", Visibility of short and tall drivers

Other disadvantages of a flat windshield angle

• Other traffic can not see the driver through the reflection if the driver can see them.
• The heater needs more time to heat the bigger window surface.
• The flat windshield angle does not let snow slide off easily.
• The driver cannot reach the whole flat window to clean it easily.

Height of the driver

Driver height can also affect visibility.

An A-pillar that is split up and haves a small triangle window (Front Quarter glass) can give a short driver visibility problems. Some cars the windshield is fillet with the roof-line with a big radius. A fillet round A-pillar can give a tall driver visibility problems. Also sometimes the A-pillar can block the driver from seeing motorcyclists.

Also the B-pillar (car) can block the vision of a tall driver in small 4 door cars.

Turning your head reduces blind spot

A driver may reduce the size of a blind spot or eliminate it completely by turning their head in the direction of the obstruction. This allows the driver to see better around the obstruction and allows the driver better depth perception.

Visibility in a convertible

Because there is no roof connection between the A- and B- pillar The A-pillars of a convertible automobile have to be stronger and even thicker,

However, with the top down there are no B or C pillars, improving driver visibility behind the driver.

Windshield reflections

Sunlight dashboard reflection

Dashboard reflection

It is best if the dashboard has a non-reflecting dark colored surface.^[4]

A small dashboard gives some reflection on the lower part of the windshield.

A big dashboard can give reflection on eye height.

A-pillar reflection

It is best if the inside of the A-pillar has a non-reflecting dark colored surface.^[4]

If the side of the window is curved there is less A-pillar reflection. ^[5]

Light through roof reflection

Some new model cars have a very big sunroof. Sometimes the sunlight through the roof lights up the dashboard and gives a reflection in the windshield.

Other automobile design factors

Other design factors may prevent a manufacturer from maximizing visibility. These include safety, as narrower pillars cannot be made strong as easily as thicker pillars, and size restraints pertaining to aerodynamics, as taller, more vertical windshields create additional drag and reduce fuel efficiency.

Rear-view mirror blind spots

Main article: Blind spot (automobile)

A vehicular blind spot is the area of the road that while driving cannot be seen when looking forward or through either the rear-view or side mirrors. Blind spots can be checked by turning one's head briefly, eliminated by reducing overlap between side and rear-view mirrors, or reduced by adding other mirrors with larger fields-of-view. Detection of vehicles or other objects in blind spots may also be aided by systems such as video cameras or distance sensors, though these are uncommon or expensive options in automobiles generally sold to the public.

See also

• Experimental Safety Vehicle (ESV)
• Pininfarina vertical A-pillar Ferrari P4/5
• Volvo SCC
• Blind spot (automobile)
• Automobile
• Automobile design
• Crash
• Car handling
• Car accident
• Rear-view mirror
• Category:Automotive safety technologies

References

1. ^ Fasimod^{[dead link]}
2. ^ "Wide-angle driver visibility and safety innovations distinguish Volvo BeeVan Truck Concept". Gizmag.com. 2007-03-09. http://www.gizmag.com/go/7081/. Retrieved 2011-11-13. 
3. ^ "Camaro - Steve Statham - Google Books". Books.google.com. http://books.google.com/books?id=YcQoGMPQspIC&pg=PA111&lpg=PA111&dq=firebird+winshield+angle+68&source=web&ots=Z9udl2jeV6&sig=auj1-zL4UFBFZJl-tAdwiYZgb9Y&hl=en&sa=X&oi=book_result&resnum=10&ct=result. Retrieved 2011-11-13. 
4. ^ ^{a b} http://esvc000873.wic017u.server-web.com/iPublish/archives/1/080.010.020/83/fs_nx_general_pack_8.pdf
5. ^ "Blind spot offenders named | Auto Express News | News". Auto Express. 2006-08-07. http://www.autoexpress.co.uk/news/autoexpressnews/202148/blind_spot_offenders_named.html. Retrieved 2011-11-13. 

• European Transport Safety Council (ETSC) [1]
• Federal Motor Carrier Safety Administration (FMCSA)
• Pedestrian Safety Through Vehicle Design
• Traffic safety
• Vehicle inspection
• Pininfarina PF Sigma (1963)[2]
• [3] Driver visibility, Volkswagen Beetle GL (1999)
• [4] The Truth About Cars /Chevrolet HHR 1LT
• [5] Research: Front-End Blind Spots Cause Accidents
• [6] Car visibility ratings revealed
• [7] Peugeot 888 concept car increases driver visibility

External links

• Volvo SCC (Safety Concept Car)
• Driver visibility in a School-bus
• Mercedes Uses Virtual Reality to Study Driver's worldview and visibility problems with the pillars. (22 jun 2007)
• "No vehicle may be equipped with more than two 'A' pillars..." (.DOC)
• Vehicle Safety Site
• European safety ratings
• European vs US roof strength
• 2003 visibility test popular European car models
• American safety ratings
• There is no regulation for minimum driver visibility jet
• National Transportation Safety Board (USA)
• NRMA Insurance rating of driver vision for Australian vehicles
• CAR design