The connection of multiple adjectives In the following sentence:


  “现在大家坐上‘复兴号’，不仅更宽敞明亮舒服、速度更快，在车上打电话的信号也更好了，这些都是能感受到的变化。” 丁荣军说，“我们正在研究怎么接入媒体，让视频也能到车上去。”


The relevant part means:


  Not only it is more spacious, lighter, and more comfortable, and faster, but the signal of the phone is also better. All of them are the changes you can sense.


Usually, the adjectives are concatenated with a conjunction, such as 和 or 并. But in this case the adjectives are not concatenated with any conjunction, and it is in the form of "ABC", not "A、B和C".

Why does it use no conjunction, and how can I know in which situations it is required to use a conjunction to concatenate adjectives.

Also, does the meaning get different if I add 和 in this case?
You do not always need 和 between adjectives.
You could use 宽敞明亮、舒服.
宽敞明亮 usually works together.

"现在大家坐上‘复兴号’，
Now (for) everyone sitting on the 'D train'

不仅更宽敞明亮舒服、速度更快，
it is not only bigger, brighter, more comfortable, faster,

在车上打电话的信号也更好了，
the phone signal in the train is also better,

这些都是能感受到的变化。”
these are all perceptible changes

丁荣军说，
Ding Rong Jun said

“我们正在研究怎么接入媒体，让视频也能到车上去。
We are researching how integrate media

让视频也能到车上去。
(and) also make video work on (the train).