I have always thought that motorways should be designed with fundamentally different approach. Kirchhoff laws state that the sum of the currents flowing to a point should equal the sum of the currents flowing from that point.
I was impressed when i first came across an on ramp in California that had a traffic light on the on ramp theoretically preventing people from entering the highway if the light was red thus controlling the number of vehicles getting onto the highway.
Where i came from it always amused me that there was unrestricted access to onramps yet just about every offramp had a traffic light at the end of it. When the lights went red, they not only stopped flow off the highway they caused backup and congestion across the entire flow of traffic. Dumping an offramp into a downtown district as happens so often is a recipe for disaster. Yet happens universally.
I dont have a clue what Caltrans was using to determine when it should be red or green but a move like this that would be incorporated in a total highway management system would make for better highway flow.
Add that to what has been proven to work on the M25 ring road around London where they have large overhead gantries that have variable speed limit signs where the speed limit is altered to suit the conditions of the traffic in the "pipe" up ahead and essentially slow down the oncoming wave to alleviate congestion and events in dense areas could be very different. They also supplement this with active variable messaging signs providing drivers with transit times and information about how long an alternative route would take.
On the M25 on the exit side of the gantry they have red light cameras and should you be travelling in excess of the front facing speed limit sign at the time you are ticket for speeding automatically. Only takes a few before you become compliant but in actual fact what makes you end up being compliant is really the fundamental improvement in your journey time and flow of traffic due to the effect the closed loop control has on the traffic and the excellent information the message boards provide about how long it will take to get to various off ramps along the way.
Thats not to say they dont have snafus but when you consider the volume of traffic it handles they minimal compared to what it used to be like in prior times with even less traffic on the highway there.
They also learnt as did many other traffic management authorities around the world, from Atlanta in 1996 when they hosted the Olympics and seriously significant dollars were put into a sophisticated traffic management center, that leaving an accident on the highway to be managed by the first police presence on the ground is a big mistake and that having a central traffic management center with fantastic live feeds showing entire highway but no communication between police on the ground and the central traffic management center is of no use.
They watched in dismay at the time as the officer on the ground caused a bigger snafu by his actions than was taking place prior to his arrival.
So on the M25 today due to sophisticated algorithms developed not only by the crown but also the US Fed Dept of Highways, they can predict an accident in the making simply based on real time traffic patterns at a point in time, the result is they actually insert a crash squad into the flow at this time in order to be on the scene and clear the jam under the control of the traffic management center asap.
There are times and circumstances where clearing the jam simply means leaving it in place and setting up clear indication of the need to bypass until the flow eases to enable moving the wreckage out the way.
Of course all this takes money to implement but it can provide an alternative to just continuously widening the road.
I personally dont think enough has been done in the use of HOV as a strategy as well as the use of moving center lane Jersey barriers to alter road configuration to suit flow of traffic. Easier said than done in some places traffic density is just way in excess of any tangible or affordable solution.