Лучше поехать домой засветло: на этой дороге ночью опасно.

Both are possible, but they mean slightly different things.

• поехать is perfective, so it presents the trip as one whole action: it would be better to set off / make the trip home before dark.
• ехать is imperfective, which would sound more like the process of traveling.

In this sentence, поехать is natural because the speaker is talking about a single decision: it’s better to leave/go home before dark.

Here лучше means it is better to... or you’d better....

It is the comparative form of хорошо (well / good), but in sentences like this it works almost like an impersonal recommendation:

• Лучше поехать домой засветло. = It’s better to go home before dark.

Russian often omits words like нам, тебе, or стоит if they are understood from context.

Russian very often leaves out the subject when it is obvious or unimportant.

So Лучше поехать домой засветло literally has no stated subject, but in English we naturally supply one:

• We’d better go home before dark
• You’d better go home before dark
• It would be better to go home before dark

The Russian sentence stays more general and context decides who it refers to.

Домой is a special adverb meaning homeward / to home / home.

Compare:

• домой = motion toward home
• дома = at home
• к дому = toward the house/building

So:

• поехать домой = to go home
• быть дома = to be at home

This is a very common Russian pattern.

Засветло means before dark, while it is still light outside, or in daylight.

It is a fixed adverb, and although it is not one of the very first Russian words learners meet, it is completely normal and useful.

In this sentence it means:

• Лучше поехать домой засветло = It’s better to go home while it’s still light / before it gets dark

It is not the same as simply днём (during the day). Засветло specifically emphasizes before darkness falls.

На этой дороге is in the prepositional case.

• дорога = road
• на дороге = on the road
• на этой дороге = on this road

The adjective этой agrees with дороге in case, number, and gender.

This phrase means on this road or on this particular road.

Ночью is the instrumental case form of ночь.

Russian often uses the instrumental case to express time when something happens, especially with parts of the day or seasons:

• утром = in the morning
• днём = during the day
• вечером = in the evening
• ночью = at night

So на этой дороге ночью опасно means it’s dangerous on this road at night.

Because Russian often uses impersonal predicative words like опасно, холодно, темно, можно, нельзя without an explicit verb in the present tense.

So:

• Опасно. = It is dangerous.
• Здесь опасно. = It is dangerous here.
• На этой дороге ночью опасно. = It is dangerous on this road at night.

In present-tense Russian, the verb to be is usually omitted.

In school grammar it is often treated as a predicative word (sometimes linked historically to a short-form adjective), and in practice you can think of it as meaning dangerous in an impersonal structure:

• Здесь опасно. = It’s dangerous here.

Compare:

• опасная дорога = a dangerous road
  
  • here опасная is a regular adjective describing a noun
• на этой дороге опасно = it’s dangerous on this road
  
  • here опасно does not describe a noun directly; it forms the whole predicate

So it behaves differently from a normal adjective like опасная.

The colon links the two parts by showing that the second part explains the first.

So the structure is:

• Лучше поехать домой засветло:
  на этой дороге ночью опасно.

Meaning:

• It’s better to go home before dark: it’s dangerous on this road at night.

In English, you might translate this with:

• a colon,
• a dash,
• or because.

Russian punctuation often uses a colon when the second clause gives the reason or explanation for the first.

Yes. Russian word order is flexible, and changing it changes emphasis more than basic meaning.

For example:

• Лучше поехать домой засветло.
  Neutral: It’s better to go home before dark.
• Засветло лучше поехать домой.
  Emphasizes before dark.
• Домой лучше поехать засветло.
  Emphasizes home as the destination.

The original order sounds natural and neutral.

Yes. That would make the sentence more explicit about who the recommendation is for.

Examples:

• Нам лучше поехать домой засветло. = We’d better go home before dark.
• Тебе лучше поехать домой засветло. = You’d better go home before dark.

Without нам / тебе, the sentence is more general and context supplies the person.

Этой is simply the normal form of этот in the prepositional singular feminine, agreeing with дороге.

Forms of этот here are:

• masculine: этом
• feminine: этой
• neuter: этом
• plural: этих

Because дорога is feminine singular, we get:

• на этой дороге

A form like этой-то would add extra emphasis, something like on this very road, but that is not needed here.