Auf dieser Straße gilt ein Tempolimit von dreißig Kilometern pro Stunde.

Because auf takes the dative here.

In this sentence, auf dieser Straße means on this street/road, which describes a location, not movement toward somewhere. With two-way prepositions like auf, German uses:

• dative for location: auf dieser Straße
• accusative for direction/movement: auf diese Straße

So:

• Ich fahre auf dieser Straße. = I’m driving on this road.
• Ich biege auf diese Straße ab. = I turn onto this road.

Since Straße is feminine, the dative form of diese is dieser.

Gilt is the third-person singular form of gelten, which often means:

• to apply
• to be valid
• to be in force

So Auf dieser Straße gilt ein Tempolimit ... literally means:

On this road, a speed limit applies.

This is a very natural and common way to express rules, laws, and regulations in German.

Examples:

• Hier gilt Rauchverbot. = No smoking applies here / Smoking is prohibited here.
• Diese Regel gilt für alle. = This rule applies to everyone.

Yes. German often puts the topic first, and then the conjugated verb must come in second position.

So:

• Auf dieser Straße gilt ein Tempolimit ...
• Ein Tempolimit gilt auf dieser Straße ...

Both are grammatically possible.

The version with Auf dieser Straße first emphasizes the location: on this particular road.

The key rule is that the finite verb, here gilt, stays in second position, not necessarily as the second word, but as the second sentence element.

German usually uses an article with countable singular nouns when speaking about one instance of something.

So ein Tempolimit means a speed limit.

You could sometimes hear article-less expressions in certain fixed official-style phrases, but in a normal sentence, ein Tempolimit is the natural choice.

Compare:

• Hier gilt ein Tempolimit von 30 km/h. = A speed limit of 30 km/h applies here.
• Hier gilt Tempolimit. = possible in a very compressed/sign-like style, but less normal in full everyday prose.

The phrase von + dative is commonly used to state the value or amount of a limit.

So:

• ein Tempolimit von dreißig Kilometern pro Stunde = a speed limit of thirty kilometers per hour

Here von means of in the sense of with a value of.

Other examples:

• eine Geschwindigkeit von 100 km/h = a speed of 100 km/h
• eine Höhe von 2 Metern = a height of 2 meters

Because von always takes the dative, you get:

• dreißig Kilometern

not dreißig Kilometer in this phrasing.

Because von requires the dative case, and Kilometer is plural here.

The plural of Kilometer is normally Kilometer, but in the dative plural, many German nouns add -n if possible:

• nominative plural: dreißig Kilometer
• dative plural: von dreißig Kilometern

So the -n is there because of dative plural.

Pro Stunde is the standard way to say per hour.

• pro = per
• Stunde = hour

So:

• Kilometer pro Stunde = kilometers per hour

This is a fixed measurement expression. In der Stunde would usually mean something more like within the hour or in the hour, not per hour as a rate.

Because all nouns are capitalized in German.

So in this sentence, these nouns are capitalized:

• Straße
• Tempolimit
• Kilometern
• Stunde

This is one of the most noticeable spelling differences from English.

Dreißig is the standard spelling in German.

The ß is called Eszett or scharfes S. In modern spelling, ß is generally used after a long vowel or diphthong, and the vowel sound in dreißig is long.

A useful thing to remember:

• dreißig = thirty
• dreißigste = thirtieth

In Switzerland, you may see ss instead of ß, so dreissig is common there.

Yes. Tempolimit is very common and natural in everyday German.

It literally combines:

• Tempo = speed
• Limit = limit

There are also more formal or technical alternatives, such as:

• Geschwindigkeitsbegrenzung = speed restriction / speed limit

But Tempolimit is shorter and extremely common in speech, news, and everyday writing.

Yes, absolutely.

In normal writing, signs, traffic rules, and everyday use, you would very often see:

• Auf dieser Straße gilt ein Tempolimit von 30 km/h.

That is probably even more common in practical contexts than spelling out dreißig Kilometern pro Stunde.

The fully written-out version is just more formal or textbook-like.

A rough breakdown is:

• Auf = on
• dieser Straße = this road/street
• gilt = applies / is in force
• ein Tempolimit = a speed limit
• von dreißig Kilometern pro Stunde = of thirty kilometers per hour

So very literally:

On this road applies a speed limit of thirty kilometers per hour.

That sounds unnatural in English, but it helps show how the German sentence is built.

It can be either, depending on context.

Straße is a broad word that can mean:

• street
• road

In this sentence, English could naturally use either:

• On this street, a speed limit of 30 km/h applies.
• On this road, there is a speed limit of 30 km/h.

The best translation depends on the situation and what kind of roadway is meant.

Because German often expresses this idea differently from English.

English might say:

• There is a speed limit of 30 km/h on this road.

German often prefers:

• Auf dieser Straße gilt ein Tempolimit ...
• literally: On this road, a speed limit applies.

So instead of using a structure like there is, German uses the verb gelten to express that a rule is valid or in force.

Not in the same way.

• auf dieser Straße = on this street/road, traveling or located on it
• in dieser Straße = in this street; sometimes possible, but usually used more like in this street named X, especially in urban contexts
• an dieser Straße = at/on this road, usually meaning next to it or along it, not on the surface as a route

For traffic rules applying to vehicles using the road, auf dieser Straße is the most natural choice.