Firstly, Bus, buses follow routes all over the city, additionally, Tnd they have separate lanes.

Some dictionaries show busses as an alternative way of writing it, but buses is way more common. In any case, you had used buses later on and it would be best to stick to one way of spelling it in your entry :)

Secondly, taxis are available whenever you need them.

Once upon a time, before the internet taxi was invented, they were more expensive.

Almost every day, I take buses to the university at least once a day as I haven’t got my own vehicle yet.

The comma is not needed here.
You could also say "I take the bus..." and it would stay singular even if you needed to transfer buses to get to your destination.

Additionally, the air is heavily polluted by exhaust fumes and traffic jams which always take place,; especially polluted by air and noise pollution.

The way you have written it makes it look like air and noise pollution are types of traffic jams. By dividing up the sentence, the meaning is made clearer.

Planes and Ttrains depart and arrive on time.

In addition, there are many convenient facilities catering and enjoyable in terms of onboard services like meals or comfortable seats, however t. Traveling by planes is, however, clearly time-saving, while traveling by trains offers you a chance to see the world outside.

Catering to...? If you were talking about providing food, then this is redundant since you tall about meals later on in the sentence so you could just remove it and gain clarity.

Your sentence clearly covered two different topics, so making it two sentences makes for clearer understanding.

And for some reason, traveling by plane, bus, car, or train is always singular even if you end up having to board different buses, transfer planes, etc. during your trip.

Firstly, Busbuses follow routes all over the city, additionally, Theynd they also have separate lanes.

Additionally, the air is heavily polluted by exhaust fumes and traffic jams, which always take place, especially air andcause noise pollution.

Planes and Ttrains depart and arrive on time.

In addition, there are many convenient facilities catering andto enjoyable in terms of onboard services like meals or comfortable seats, h. However, traveling by planes is clearly time-saving, while traveling by trains offers you a chance to see the world outside world.