I do not agree that the speed limit should be increased to 120km/hr. I remember reading, a while ago, that roads are engineered for a certain speed. I don't think ours are engineered, safely, for speeds of 120km. I drive up and down the highway, fairly regularly, and 120km does not leave any space for error. It's dangerous. We have people and animals crossing our highways. 120km will not allow you enough braking time in one of these unforeseen instances.
In the UK, the maximum speed on the motorways is 70mph (112km/hr). Their pristine motorways. In the US the maximum speed is 75-85mph ( 121-137km/hr) in the western states. It's 70mph ( 110km/hr) in the eastern states. Puerto Rico has a speed limit of 65mph (105km/hr). Hawaii's limit is 60mph (97km/hr).
It has been shown, by the Norwegian Institute of Transport Economics, that increasing the speed limit in the 15-75mph (25-120km/h) range, will increase crashes and the severity of the injuries in said crashes. Reducing the speed limit will have the opposite effect. Speeding is a problem all over the world. We compound it by adding alcohol and tailgating, and sheer insanity into the mix.
Speed limits are set for the upper limit of favourable road conditions. People should use their common sense and adjust their speed according to the current conditions.
There are several factors which have to be considered for safe speeds. The condition of the vehicle and the capability of the driver. The volume of traffic. The weather and available sight distance. And finally the road design. It's function. The lane and shoulder widths, and it's horizontal and vertical curves. (This information was found in the US Ministry of Transport web site).
Taking all of the above into consideration, and the reckless way in which some of our people drive, then I believe 100km/hr ( 62.137mph) might be a more realistic limit. This will take the road condition into consideration for increased mobility safely. This limit should be for cars. Heavy duty vehicles should have their own limit. However, it should be the design of the road which determines our speed limit, not us.
Anne Murphy