Merge!

The same number of cars are getting through but in a smaller space.

Therefore, each must be moving faster in the narrower section. It's similar to water moving faster in the section of hose that has a kink in it or is being pinched.

I think we can relate this to fluid flow.

Equation of continuity states, $A_1v_1 = A_2v_2$ i.e, Velocity of a fluid is inversely proportional to the area of cross section.

Since, Area of narrow path is small compared to wider one, the cars should move faster there.

Is this even right way of answering this?

The vehicles merging are anticipating the single lane of traffic, therefore they are accelerating slowly. If this precaution is ignored by a speeding driver, the driver runs the risk of missing the merge. Thus it is important to the imagination: the vehicles merging are significantly slower than the vehicles already merged into the single lane of traffic.

In the wider space, people have room to change lanes and do things like that so that should slow down the traffic. So in a narrower space the cars are moving in a more uniform way

The space is narrower but the number of cars is the same. So the cars will have to move faster.

This was an easy one for me because of my fluid dynamics course and my experience merging into the Queens-Midtown Tunnel in New York!

The assumption is that the cars do not wait (in contrast to the regular traffic). In such a case, the average velocity in the narrow section will have to be not just higher, but exactly double that of in the wider section, as double the number of cars have to pass through bumper-to-bumper

Cars have to slow dowm when merging together so there is traffic jam in the merging part.

In the wider path the cars can move slow because it has more space.But in the narrow path the cars need to move faster than in wider path.

This is similar to fluids mechanics

In order to do a zipper merge (the proper way to merge lanes- one car from each lane in a back and forth pattern), the flow of traffic must slow down to accommodate the car in the next lane going into the narrow lane. That's how I thought of it at least!

When you’re waiting to merge, you are waiting for someone else beside you to take their turn, and every person who gets to the bottleneck has to spend half their time waiting, which cuts your speed in half. When the car gets to the bottleneck they’re free and clear because they can go as fast as they want under the bridge (with the limitation being the driver in front of them and of course the law) and the single file line of people coming from the bottleneck are the only traffic on the other side. Especially if there is not a stoplight ahead.

I feel that, (assuming normal situation ) as there can be more than one car at the wider section so the chances of collision are more and to avoid it driver has to slow down the car and at narrower section , due to single lane , probability of the occurance of second car is negligible and psychologically driver feels it as no risk situation...

For the two lane traffic merging into one lane as shown in the figure, cars on the wide part would be waiting half the time in the queue for cars on either lanes to merge, but once merged, the traffic should flow twice as before the merge, hence one would expect that cars should be moving faster in the narrow part.