No vale la pena viajar en tren durante los feriados.

No vale la pena means it’s not worth it or it’s not worthwhile.

The full expression is valer la pena, which literally looks like to be worth the trouble / the effort. In real use, you can think of it simply as to be worth it.

Examples:

• Vale la pena estudiar español. = It’s worth studying Spanish.
• No vale la pena discutir. = It’s not worth arguing.

In your sentence, No vale la pena viajar en tren durante los feriados, the idea is:

Traveling by train during the holidays is not worth it.

Because valer la pena is a fixed expression. You learn it as a whole chunk:

• valer la pena = to be worth it

So even though English just says worth it, Spanish uses the full expression with the article:

• Vale la pena
• No vale la pena

You generally should not remove la here.

Because after vale la pena, Spanish often uses an infinitive to say what action is or is not worth doing.

Structure:

• vale la pena + infinitive

So:

• Vale la pena viajar = It’s worth traveling
• No vale la pena esperar = It’s not worth waiting
• No vale la pena viajar en tren durante los feriados = It’s not worth traveling by train during the holidays

This is very similar to English It’s worth + -ing, but Spanish uses the infinitive instead.

Because the expression is functioning impersonally here.

Spanish often uses vale la pena + infinitive as a general statement:

• Vale la pena intentarlo.
• No vale la pena discutir.

Even though viajar en tren durante los feriados is the idea being evaluated, Spanish commonly keeps vale in the singular in this kind of impersonal construction.

You can think of it like:

• It is worth it to travel... rather than
• Traveling ... are worth it

So singular vale is the normal form.

En tren is the normal way to say by train.

In Spanish, transportation is often expressed with en:

• en tren = by train
• en avión = by plane
• en autobús / en bus = by bus
• en coche / en carro / en auto = by car

So:

• viajar en tren = to travel by train

You may sometimes hear por tren in certain contexts, but en tren is the standard choice for means of transportation.

Feriados means holidays in the sense of public holidays / official holidays.

This does not usually mean a vacation period in general. It refers more to calendar holidays such as national holidays, long weekends, and official days off.

So:

• los feriados = the holidays / public holidays

This is especially common in much of Latin America. Depending on the country, people may also say:

• días feriados
• festivos
• días festivos

It is not exactly the same as vacaciones, which means vacation or school/work break.

Because Spanish often uses the definite article with general time periods or categories when English may not.

So:

• durante los feriados = during the holidays

The article los helps identify the period as a known type of time: the holiday period.

You will often see this in Spanish:

• durante el verano = during the summer
• en los fines de semana = on weekends
• durante las vacaciones = during vacation / during the vacations

This is a very common question.

• feriados = public holidays, official days off, holiday dates on the calendar
• vacaciones = vacation, break, time off for travel/rest, often longer

Examples:

• Durante los feriados hay mucho tráfico. = During the holidays / public holiday period there is a lot of traffic.
• Durante las vacaciones fuimos a Perú. = During vacation we went to Peru.

So in your sentence, feriados suggests crowded travel dates, which fits the idea that train travel is not worth it then.

Durante means during, so durante los feriados is a very direct translation of during the holidays.

Yes, in many cases en los feriados could also be understood, but durante emphasizes the whole time period more clearly.

Compare:

• durante los feriados = during the holiday period
• en los feriados = on/in the holidays

For this sentence, durante los feriados sounds very natural.

Usually, no—not if you mean train travel in general.

• en tren = by train, as a means of transportation
• en el tren = on the train, inside a specific train

So:

• viajar en tren = to travel by train
• estar en el tren = to be on the train

If you say en el tren, it sounds like you are referring to a particular train, not the general mode of travel.

Yes. Spanish word order is fairly flexible here.

These are all possible:

• No vale la pena viajar en tren durante los feriados.
• Durante los feriados, no vale la pena viajar en tren.
• Viajar en tren durante los feriados no vale la pena. (less common, but understandable)

The original version sounds very natural and neutral. Moving durante los feriados to the front puts more emphasis on the time period.

Yes, generally vale la pena is the safer and more widely useful choice for Latin America.

Both mean to be worth it, but:

• vale la pena is very common across the Spanish-speaking world
• merece la pena is also correct, but many learners associate it more with Spain

So for Latin American Spanish, vale la pena is an excellent expression to learn first.

Yes, but it means something slightly different.

• No vale la pena viajar en tren durante los feriados.
  = It’s not worth traveling by train during the holidays.
  This is a general statement.

• No vale la pena que viajes en tren durante los feriados.
  = It’s not worth your traveling by train during the holidays / It’s not worth it for you to travel by train during the holidays.
  This sounds more directed at a specific person.

So:

• infinitive = more general
• que + subjunctive = more specific, often aimed at someone

Since viajes is in the subjunctive, that version is grammatically a bit more advanced.

It does not necessarily mean trains are bad. It means the speaker thinks traveling by train during the holiday period is not worthwhile.

That could be because:

• trains are crowded
• tickets are expensive
• delays are common
• stations are chaotic
• the effort is not worth the benefit

So no vale la pena expresses an overall judgment, not just one specific problem.