The purpose of the ramp is to get up to a speed that matches the flow of traffic on the main road. Matching speed allows safe merging. There can be no denying that trying to join the main carriageway at 30 mph when the traffic flow is 60 mph is highly dangerous.
However, the traffic on the main carriageway has the right of way, and traffic merging MUST yield to traffic that is already on the main carriagway. If you are preparing to join the main carriageway but traffic speed and heavy volume prevent you from finding a space, then you MUST slow down or stop. If you do stop at the merge line, then when you do join it must be with exceptional care, during a suitably large gap in traffic.
This should not be a frequent occurance, as in most cases you should have adequate warning that a merge will be difficult and be able to find a suitable space. However, in 10 years, I have once had to perform this maneouvre.
What I have seen several times, and is exceptionally dangerous, is some idiot realise that they cannot join and then drive onto the shoulder to try and join further up. The shoulder is only for emergency use - careering down it at 70 mph while looking to join the main carriageway is crazy - because the shoulder is the one place on a highway where you can EXPECT there to be stationary vehicles.
Of course, even I'm boggled by the stupidity shown by some drivers - as illustrated by this quote taken from earlier in the thread.
This guy in a fairly new Trailblazer was going down an onramp at about 35 mph. He was talking on his phone. By the time we get to the interstate there are a series of tractor trailers and no way for them to get over. They begin to slow down to let him speed up and merge in front of them and yes by this time we are in the emergency lane. So what does he do but SLOW down. That?s when I opened up and went around his ass in the damn grass and gravel throwing rocks all over his SUV ( I was driving a 4.3L V6 S10). I then went back onto the emergency lane and merged ahead of the tractor trailers.
To deliberately drive off road, then drive down the emergency lane (cutting in front of someone who is obviously a poor driver) is lunacy. You put yourself and your vehicle at risk by driving in unpredicatable conditions, and you perform a dangerous manoeuvre in front of an unskilled driver - potentially inducing them to make a critical mistake. All because of your impatience and arrogance.
What you should have done as soon as you realised that the driver in front was incompetant and trying to join at low speed, was to slow down and give them space to join. This will also give you space to accelerate up to a safe joining speed, when you decide to begin this maneouvre. You reduce the pressure on the poor driver, you provide a safety margin for yourself incase they cause an accident, and you provide opportunity to perform the manouevre safely yourself.