How does this に in 走行中に work here?

Question

For full context: https://www3.nhk.or.jp/news/html/20180617/k10011481821000.html?utm_int=news_contents_news-main_001

The sentence in question: ＪＲ東日本によりますと、17日午後２時前、午後０時20分に東京を出発し、新函館北斗に向かっていたはやぶさ21号と秋田に向かっていたこまち21号が、宮城県の仙台と古川の間を走行中に非常ブレーキが作動し、緊急停車しました。

My attempt at translation: "According to JR east Japan, on the seventeenth before 2p.m (??? 午後０時20分に ???), the hayabusa21 which left tokyo and headed towards shinhakodate-station and the komachi21 which headed towards Akita had an emergency break while in motion through the area of an old river and Sendai City in miyagi prefecture."

So 走行中 is listed as a の-adjective https://jisho.org/search/%E8%B5%B0%E8%A1%8C%E4%B8%AD but my textbooks never told me that に can be applied to them ^^ I guess it does the same thing as with な-adjectives? Making them an adverb? I could imagine interpreting に very fundamentally as "in" like "in motion", however then it would only reinforce the basic meaning of 走行中 and furthermore, there is a preceding を. This を reminds me of the を you can see in 橋を歩く for example, but I'm not sure wether I can put it into relation to the 非常ブレーキが作動し phrase since that one seems rather isolated to me...

Answer 1

How does this に in 走行中に work here?

As @user4092 mentioned, に can be used to denote a point in time or a duration of time. Also, ○○中 can be used to denote a time period during which ○○ is happening. Therefore, ○○中に functions as an adverb, and ○○中の functions as an adjective.

furthermore, there is a preceding を

This is similar to the を in the 橋を歩く that you mentioned.

をrefers to 走行 in （宮城県の仙台と古川の）間を走行（する）. This means "travel the interval between Sendai and Furukawa".

So,

「．．．はやぶさ21号と．．．こまち21号が、仙台と古川の間を走行中に．．．」

means (omitting the words represented by ellipses)

...while Hayabusa 21 and Komachi 21 were traveling between Sendai and Furukawa...