I just happen to feel that the 30 limit is the most important, since it is usually in built up areas where there is a greater chance of a pedestrian running out.
And herein lies the reason so many people speed...
In built up areas where there is a good chance of kids playing in the street, and thus running out into the road, sticking to 30 or less is a must.
But so many streets in this country have inappropriate speed limits, why do the 20 limits outside schools still apply at night and during school holidays? Why are the city dual carriage ways 30 or 40 limits? Heck why is the dual carriage way and motorway speed limit only 70 when modern cars are capable of speeds far faster than this perfectly safely?
If the speed limits were actually set to safe speeds for the roads, rather than the arbitary levels they are set to now then I am sure the vast majority of people who speed now wouldn't speed.
- Dual carriage ways and motorways 90-100 mph
- City dual carriageways 70 mph
- Main trunk roads 70 mph
- Main routes into towns and cities 60mph (Where houses are set back behind long drives or are on parallel side roads) 60 mph
- Main roads in built up areas 30 mph (40 at night)
- Housing estates, outside schools etc. 20 mph (30 at night)
Where a major traffic route also is likely to have heavy pedestrian traffic too, but barriers up along the pavement edge and install pedestrian crossings to allow their safe passage across the roads.
On all those country trunk roads where you get side roads joining in stupid places with no visibility, move the joinging point to where visibility is good, or simply close it off and re-route people to the next side road instead, their usually joined up.
But then applying logic to road safety has never been something the government has been capable of, it requires far less thought to just reduce speed limits.