bǐqǐ zài chēguǎnsuǒ qǔhào, wǎngshàng huànzhèng gèng fāngbiàn.

The basic pattern is:

比起 A，B 更 + adjective

So here:

• A = 在车管所取号
• B = 网上换证
• adjective = 方便

That gives:

Compared with A, B is more convenient.

More literally, the sentence is organized like this:

• 比起在车管所取号 = compared with taking a queue number at the vehicle administration office
• 网上换证 = renewing/replacing the license online
• 更方便 = is more convenient

So the sentence means something like:

Compared with going to the vehicle administration office and taking a number, renewing the license online is more convenient.

比起 means compared with or when compared with.

It is closely related to 比, but there is a slight difference in feel:

• 比 is the standard comparison marker:
  A 比 B 方便 = A is more convenient than B
• 比起 often introduces the thing you are comparing against, especially when that part is long:
  比起A，B更方便 = Compared with A, B is more convenient

In this sentence, 比起 sounds natural because A is not just one noun; it is a whole action phrase: 在车管所取号.

So:

• 网上换证比在车管所取号更方便 = also grammatical
• 比起在车管所取号，网上换证更方便 = a little more topical, like as for comparing it with...

在 marks location.

So:

• 在车管所 = at the vehicle administration office
• 在车管所取号 = take a number at the vehicle administration office

Chinese often uses 在 + place + verb to show where something happens.

Examples:

• 在家吃饭 = eat at home
• 在学校上课 = have class at school
• 在车管所取号 = take a queue number at the DMV / vehicle office

Without 在, the location relationship would be unclear or unnatural here.

车管所 is short for 车辆管理所.

It refers to the government office that handles vehicle- and driver-related paperwork, such as:

• license renewals
• registration matters
• driving test administration
• plate-related procedures

A very natural English approximation is the DMV or the vehicle administration office, depending on context.

So in this sentence, 车管所 is the office where people would traditionally go in person to handle the license matter.

取号 literally means to get a number.

In service settings in China, it usually means:

to take a queue number / to get a ticket number / to pull a number

For example, at a bank, hospital, or government office, you often first take a number and then wait until your number is called.

So 在车管所取号 does not mean getting a phone number or ID number. It means getting your place in line.

Both are possible.

• 网上换证 = renew/replace the license online
• 在网上换证 = renew/replace the license on the internet

In modern Chinese, 网上 often works almost like an adverbial location by itself, especially in everyday speech and writing.

So:

• 网上买东西
• 网上申请
• 网上换证

are all very common.

Adding 在 makes it slightly fuller and more explicit:

• 在网上买东西
• 在网上申请
• 在网上换证

In this sentence, 网上换证 sounds concise and natural.

换证 literally means to change/replace a certificate/document.

In real-life administrative use, it often means:

• renew a license
• replace a license
• exchange an old document for a new one

The exact English translation depends on context.

Because this sentence mentions 车管所, 证 probably refers to a driving-related document, such as:

• 驾驶证 = driver’s license
• sometimes another vehicle-related permit/document

So 换证 here is best understood as renewing or replacing the license.

Chinese often omits the full noun when the context makes it clear. Instead of saying 换驾驶证, it may simply say 换证.

更 means more.

In comparison sentences, it often appears before the adjective:

• 更方便 = more convenient
• 更便宜 = cheaper / more inexpensive
• 更容易 = easier

In this pattern:

比起A，B更方便

the 比起 part sets up the comparison, and 更 marks the degree on the adjective.

Could you sometimes omit 更? Yes, in some contexts Chinese can still be understood without it. But here 更方便 is the most natural way to say more convenient.

Not perfectly, and that is normal.

A very literal thinker might expect something more symmetrical, such as:

• 比起去车管所办理换证，网上换证更方便

That would compare:

• handling the renewal in person at the office
• handling the renewal online

But the original sentence uses 在车管所取号, which highlights a very typical annoying part of the offline process: going there and taking a queue number.

So the sentence is not trying to make a perfectly technical comparison. It is making a practical, everyday one:

Compared with the hassle of going to the office and queuing, doing it online is more convenient.

This kind of slightly shortened comparison is common in natural Chinese.

Yes, in a sense.

Chinese often leaves out subjects when they are generic or obvious from context.

The main clause is:

网上换证更方便

That part itself already has a subject-like element: 网上换证.

So the sentence does not need something like 这件事 or 这样做.

English often wants a more explicit subject, but Chinese is comfortable with the action phrase itself serving that role:

• 网上换证更方便 = renewing online is more convenient

This is very normal Chinese grammar.

The comma separates the comparison phrase from the main statement:

• 比起在车管所取号， = compared with taking a number at the office,
• 网上换证更方便。 = renewing online is more convenient.

It helps the reader hear the pause and understand the sentence structure more easily.

In very short informal writing, Chinese commas are sometimes omitted, but here the comma is helpful and natural because the first part is a setup phrase.

Yes. A few natural alternatives are:

• 网上换证比在车管所取号更方便。
• 比起去车管所换证，网上换证更方便。
• 在网上换证比去车管所办更方便。

These all express roughly the same idea, but with slightly different focus:

• 比起在车管所取号... emphasizes the in-person queueing experience
• 比起去车管所换证... makes the comparison more parallel
• 在网上换证比去车管所办更方便 sounds very conversational

So the original sentence is natural, but it is not the only way to say it.