Hon säger att tåget är mer pålitligt än bussen på vintern.

Hon is the subject pronoun, meaning she.

In this sentence, hon is the person doing the action of saying, so Swedish uses hon.

• hon = she
• henne = her

So:

• Hon säger ... = She says ...
• Jag ser henne. = I see her.

In Swedish, verbs do not change according to the subject the way they do in English.

So you say:

• jag säger = I say
• du säger = you say
• hon säger = she says
• vi säger = we say

The form säger is simply the present tense form for all persons.

Att here means that and introduces a subordinate clause.

So:

• Hon säger att ... = She says that ...

In English, that is often omitted:

• She says the train is more reliable ...

In Swedish, att is very common and usually sounds natural here.

Because Swedish often uses the definite singular when talking about something in a general class sense.

So here:

• tåget = the train
• bussen = the bus

This does not necessarily mean one specific train and one specific bus. It can mean train travel versus bus travel in general.

Also, the endings show the noun gender and definiteness:

• ett tåg → tåget
• en buss → bussen

So this sentence compares the two forms of transport as categories.

The basic adjective is pålitlig = reliable.

But tåg is an ett-word:

• ett tåg

When an adjective describes an ett-word in the singular, it usually takes -t:

• ett pålitligt tåg = a reliable train

The same agreement happens after är as well:

• Tåget är pålitligt. = The train is reliable.

That is why the sentence has pålitligt and not pålitlig.

Both patterns exist in Swedish for comparatives:

• -are ending: snabb → snabbare
• mer + adjective: mer intressant, mer pålitligt

With longer adjectives, Swedish often prefers mer + adjective. So mer pålitligt sounds very natural.

You may also hear pålitligare, which is possible, but mer pålitligt is very common and often feels smoother.

Important: you do not combine both forms.

• correct: mer pålitligt
• correct: pålitligare
• not correct: mer pålitligare

Because Swedish, like English, often leaves out repeated words when they are understood.

So:

• tåget är mer pålitligt än bussen means
• the train is more reliable than the bus is

The verb är is understood after bussen, so it does not need to be repeated.

This is a normal kind of comparison in Swedish.

På vintern is the normal Swedish expression for in winter / during the winter.

So:

• på vintern = in winter
• på sommaren = in summer

This is an idiomatic time expression. You usually just learn it as a set pattern.

A useful contrast:

• på vintern = in winter, generally
• i vinter = this coming winter / this winter

So in your sentence, på vintern means winter as a general season, not one specific upcoming winter.

Sometimes, especially in informal speech, Swedish can omit att after verbs like säga, just as English often omits that.

So you may hear:

• Hon säger tåget är mer pålitligt än bussen på vintern.

But the version with att is clearer and more standard:

• Hon säger att tåget är mer pålitligt än bussen på vintern.

For learners, it is usually safest to keep att.

This is a very common question because Swedish word order changes in subordinate clauses.

After att, the clause is subordinate, and inte usually comes before the verb:

• Hon säger att tåget inte är mer pålitligt än bussen på vintern.

Compare that with a main clause:

• Tåget är inte mer pålitligt än bussen.

So the pattern is:

• main clause: subject + verb + inte
• subordinate clause: subject + inte
  • verb

That is why it would be att tåget inte är ...

It describes the whole statement: during winter, the train is more reliable than the bus.

So the idea is:

• In winter, the train is more reliable than the bus.

It does not mean that only the bus is somehow in winter. The time phrase applies to the comparison as a whole.

If you want, I can also break the sentence down word by word or show a few natural variations of it in Swedish.