No toques el claxon en cada curva y no intentes adelantar si hay tanta niebla.

Because this is a negative command addressed to tú.

In Spanish, negative commands for tú use the present subjunctive:

• tocar → toques
• No toques = Don’t touch / don’t sound / don’t use

Compare:

• tocas = you touch / you sound (statement)
• toca = he/she touches or touch! for usted
• toques = subjunctive form, used here in the negative command no toques

So:

• No toques el claxon = Don’t sound the horn

For the same reason: it is also a negative tú command, so Spanish uses the present subjunctive.

From intentar:

• intentas = you try
• intentes = subjunctive
• No intentes = Don’t try

So both parts follow the same pattern:

• No toques...
• No intentes...

This is very common in Spanish:

• No hables.
• No corras.
• No lo hagas.

Normally, each negative verb needs its own no.

So Spanish says:

• No toques el claxon y no intentes adelantar...

That sounds natural because there are two separate commands:

1. Don’t sound the horn
2. Don’t try to overtake

In some contexts, Spanish can avoid repeating things, but here repeating no is the normal and clear choice.

Yes, claxon is a common word in Spain for a vehicle horn.

A learner might also meet:

• el claxon — very common in Spain
• la bocina — more common in many parts of Latin America
• la corneta — can also be used in some places

So if you are learning Spanish from Spain, claxon is a very useful word to know.

Also note that Spanish often says tocar el claxon for to honk / sound the horn.

Spanish often expresses this idea with a verb + noun combination:

• tocar el claxon
• literally: to touch/play the horn
• naturally: to honk / sound the horn

This is very normal Spanish usage. Languages do not always package actions into words in the same way.

Other similar cases:

• dar un paseo = to take a walk
• tener hambre = to be hungry
• hacer una pregunta = to ask a question

So even if English uses one verb, Spanish may prefer a different structure.

Because en works naturally here to mean at or on each curve/bend of the road.

• curva = curve, bend
• en cada curva = at every bend / on every curve

This expresses location or the point at which the action happens.

So:

• No toques el claxon en cada curva
  = Don’t sound the horn at every bend

Using a here would not sound natural in this sentence.

Here adelantar means to overtake / to pass another vehicle.

Spanish can use adelantar without stating exactly what is being overtaken, because the road context makes it obvious.

So:

• No intentes adelantar = Don’t try to overtake / Don’t try to pass

If you want to be more explicit, Spanish can add the object:

• No intentes adelantar a otros coches.
• No intentes adelantar al camión.

But leaving it out is perfectly normal when the meaning is clear.

Because after si meaning if, Spanish normally uses the indicative, not the subjunctive, when talking about a real or possible condition.

So:

• si hay tanta niebla = if there is so much fog

This is the normal pattern for real present conditions:

• Si llueve, no salimos.
• Si tienes tiempo, ven.
• Si hay niebla, no conduzcas rápido.

You would use a different structure for unreal or hypothetical situations:

• Si hubiera tanta niebla... = If there were that much fog...

So hay is correct here.

Both are possible, but they are not exactly the same in tone.

• mucha niebla = a lot of fog
• tanta niebla = so much fog / that much fog

Tanta often adds emphasis. It suggests that the amount is noticeably high and relevant to the warning.

So:

• si hay mucha niebla = if there is a lot of fog
• si hay tanta niebla = if there is so much fog

In this sentence, tanta makes the warning feel stronger.

Spanish treats niebla as an uncountable noun here, just like English treats fog.

So you say:

• hay niebla = there is fog
• hay mucha niebla = there is a lot of fog
• hay tanta niebla = there is so much fog

That is why it stays singular.

You would not normally say nieblas in this kind of road-warning sentence.

Hay is the impersonal form of haber meaning there is / there are.

So:

• hay niebla = there is fog
• hay tanta niebla = there is so much fog

This is one of the most common structures in Spanish for saying that something exists or is present.

Compare:

• Hay un coche. = There is a car.
• Hay coches. = There are cars.
• Hay niebla. = There is fog.

Yes. The forms toques and intentes show that it is addressed to tú, the informal singular you.

So this is the kind of sentence you would use with:

• a friend
• a family member
• someone you address informally

If you wanted the usted version, it would be:

• No toque el claxon en cada curva y no intente adelantar si hay tanta niebla.

If you wanted the vosotros version, common in Spain, it would be:

• No toquéis el claxon en cada curva y no intentéis adelantar si hay tanta niebla.

Because Spanish usually needs the article with nouns in this kind of structure.

So Spanish says:

• tocar el claxon

not normally:

• tocar claxon

This is a common difference from English. Spanish often uses articles where English does not.

A few examples:

• Me duele la cabeza. = My head hurts.
• Abre la puerta. = Open the door.
• Toca el claxon. = Sound the horn.

So the article is part of the natural Spanish expression.

Yes. Grammatically it is a command, but in real use it can function as:

• a direct order
• a warning
• a driving instruction
• a rule or guideline

That is very common with the imperative in Spanish. It does not always sound harsh; it often just gives practical instructions.

In a road-safety context, No toques... and No intentes... sound like standard advice or rules.