The offence of obscure vision is nothing to do with Sat Navs & Mobile Phones. It's a much older offence and relates to many things in a motor vehicle, and still does.
Degrees of offence almost always culminate in a 'Dangerous' offence and this is no different. In life as in Driving a Motor Vehicle we all do things we either are not supposed to do or do it in such a way that we convince ourselves that its 'Ok' Such as doing 50mph in that 40mph limit late at night because “you know I always do it and I have never been caught or had a crash, so it's ok, isn't it?” and the one that relates to this subject …. “I can see ok, that phone / sat nav is not blocking my view” The fact that you are moving your head / seat position to look over / around / under the obstruction in question is neither here nor there! But it is!! Lets step back a bit and talk about what obscures your vision outside of the 'new' gadgets that have taken over our lives. Hanging objects. I have seen all manner of things hanging from the rear view mirror. Badges being one of them, souvenirs from a holiday, small pictures in frames, unused CDs, lanyards & necklaces the list is endless. These form a vertical barrier to full vision which draws your focus as its in the foreground and can easily obscure a person or a cycle. Reflection! The reason the majority of dashboards, if not all, are black or dark grey is to reduce reflection onto the slanted piece of glass above it (The Windscreen for any confused parties). Anything white / light coloured is therefore a hazard as it reflects into your vision, again being in the foreground it takes your focus.
Have a look at all those items you see on dashboards, map books, work records, receipt pads, newspapers.
Not to mention many other objects all of which are hazards in other ways. In the event of a collision or sudden braking where are these items going to go? Hitting you in the face? Becoming trapped in the drivers foot well, under your feet or the pedals? The same can be said for lighting inside the vehicle, especially brighter more modern LEDs, I constantly see cars being driven at night with internal lights on, this reflects into your view and restricts your vision.
When I was in the Royal Navy going on watch onto the Bridge at night it was vital to be able to see clearly as soon as possible. It takes the human eye least 40mins to achieve good night vision in total darkness. That's why all the lights prior to reaching the Bridge were red; to artificially improve your vision as you went on watch. Dramatically reducing that 40 minute window. Driving in London is not obviously the same as the Atlantic, but your night vision certainly adjusts to low light dusk levels / street lights / headlights etc. So driving a vehicle with a bright light on inside at night will affect your vision.
Ice & Frost Goes without saying that you should completely clear the screen before driving your vehicle.
Condensation This is a major hazard to seeing clearly and is very common in older cars as well as cars using then not using air con systems. The VERY worst thing you can do is touch the inside of the screen with your hand, as you deposit grease from your skin onto the moisture. Oil and water don't mix but it does reflect light and distort vision. Even more so in wet conditions at night with water on the outside of the screen reflecting light from cars and street lights you then add further reflection and distortion inside the windscreen. Keep those fingers and hands off the screen. A moisture catcher is ideal for older cars with a moisture problem easy to get hold of at car spares shops. A roll of kitchen towel or demister pad should be the only items used to clear the screen, and be done when the vehicle is stationary whilst using the vehicles blower etc. Make sure you get rid of any wet kitchen towel as it will continue to add moisture if left in the vehicle. Cleanliness of the inside and outside. Everyone understands the importance of good wipers and a clean screen outside (hopefully), but a common problem is dirt on the inside. This is built up from various sources, dirty air from outside, smokers (including electronic cigs), sunlight (this occurs when very hot sun deteriorates the surface of the dashboard plastic as well as the cleaning products used on it – this in turn deposits itself on the inside of the screen).
Next time you are behind a vehicle with strong sunlight ahead, have a look through at the state of some peoples windscreens and then think how badly it restricts their view.
Understanding point of view The positioning of gadgets on the screen WILL lead to a loss of vision in one or more direction. This is regardless of your height / seating position / size of vehicle. If you add something it blocks your view. Most if not all devices are positioned for convenience to see or touch or both. The A post, the part of the car either side of your windscreen is already affecting your vision in particular on the right with a right hand drive car (see diagram below).
Other than phones and phone holders I have seen Sat Navs, Dash Cams and just last week a Heathrow airport feeder park device placed smack bang in the middle of the windscreen half way down. Amazing that a professional driver would think that was ok. To be sure that you are not affecting your view ahead and to the side you should fit devices to the dashboard vents or literally on the bottom of the windscreen. However caution should be exercised when not only positioning the holder of the device but also where the device itself will sit and its size; some new phones are huge. On the offside, alongside the A post is unacceptable as you are adding more loss of vision to the right, already affected by the A post. This is also a prime target for theft if your window is open it is easily grabbed by a passing pedestrian, cyclist or scooter rider. I am also regularly challenged about the height of the device on the screen, as I have said before looking around or over it is not acceptable, not legal and dangerous. In particular with a London Cab being higher than a normal car you are restricting your vision of the front offside corner of your vehicle. Do a reverse test. Sit someone in your vehicle, go out in front and walk back looking at the driver. Note how their face is obscured by any device. If it is move it! Try this looking at oncoming vehicles as you drive around. Shocking once you notice.
I hope that the above has been of use to anyone reading it. There is always an element of interpretation with Dangerous Condition Offences. However with a photograph of any device in situ you will be hard pressed to defend yourself. I must also stress the importance of the next point. This info has two aims. One to try and ensure that you don't get points on your licence and in so far as that, you yourself have the biggest interest in keeping your licence & your livelihood intact. Two, and this is the most important one, in the event of a tragic event that any of you are involved in, the investigation of any serious or fatal collision will pick apart every aspect of how you drive, how you maintain your vehicle, how you position any devices and store any item within your vehicle. On a day to day basis with the lack of Traffic PCs, and the overburdened local officers, drivers get away with many offences. But if ever there was a targeted campaign against phone use / phone positioning, on the same scale as previous Seat Belt, Speeding or Insurance enforcement campaigns then many drivers, especially PHV & Taxi drivers would fall foul of that enforcement. As I used to say to many drivers I stopped and dealt with. If the person you love most in the world is crossing the road ahead of my vehicle. How do you want me to be driving? Paying attention? Driving safely? Having a clear view of the road? Or would it be ok to be staring at a map or reading a text message? You know the answer. Be Lucky, keep that licence clean and the professional standards high.