As pace of life quickens things tend to change fast in the city.

【翻译】随着生活节奏的加快，城市的变化会日新月异。

无论从意思，还是用法看，as 在这里表示时间，不表示原因。

▲ as 既可以表示原因，又可以表示时间。这需要根据“状态谓语”还是“动作谓语”，来判断它属于哪种意思：

1. as 表示时间时，是指两件事情同时发生：“在…的同时”。而且，在as 从句中的谓语动词往往表示动作性，不表示状态性（如be，have 等动词）。例如：

She wept as she spoke. 她边说边哭。

Another policeman has been injured as fighting continued this morning. 今早又有一名警员在冲突进行中受伤。

2. 在as 从句中，谓语动词若表示状态（如be,have 动词的各种形式），往往表示原因。例如：

As he was still hungry, he gobbled up a second sandwich.  因为还饿，他又狼吞虎咽地吃了第二块三明治。

I didn't mean to take a taxi but I had to, as I was late. 我虽然不想坐计程车，但因为太迟了所以非坐不可。

As he was the first transgressor, he saw no hopes of pardon. 由于他是第一个犯法者，他看不到被豁免的希望。

As he was hard up he had to take this job. 由于手头儿紧，他不得不接受这份工作。

As he was not well, I decided to go without him. 因为他身体不好，我决定独自去了。

As I had plenty of money I was able to help her. 因我的钱宽裕，我能帮助她。

As he was always cheerful he had the nickname Smiler. 他因为总是快快乐乐的，所以得了个外号叫乐乐。

He did not want to upset his father, especially as his mother was so ill. 他不想去烦父亲，尤其是因为母亲病得很重。

There’s never a dull moment in our house, especially as there are ten of us living here. 我们的房子里从都不会有片刻枯燥无聊的，尤其是因为这里住着我们十个人。

▲ as 表示时间的例句：

He was cheered as he got on the rostrum. 他走上主席台时受到群众的欢呼。

Many women, especially as they get older, develop lumpy veins in their legs.  许多妇女，尤其是年纪大了以后，腿上会现出疙疙瘩瘩的青筋。

The police picked him up as he was trying to leave the country. 他正要离开该国时，警方把他捉住了。

He butted his head against the shelf as he was getting up. 他起来时一头撞在搁架上了。

I caught him just as he was leaving his office. 他正要离开办公室时我碰上了他。

The rear tyre blew out as he was driving to work. 他开车上班时后胎爆裂。

He pointed at the map as he was speaking. 他讲话时指点着地图。

He was measuring me with his eye as he spoke. 他一边讲话，一边打量着我。

As I was waiting for a bus a brick fell on my head. 当我在等公共汽车时，一块砖头落到了我的头上。

【另外两个问题】

1. pace 表示“速度”，是可数名词，需要加冠词。本句可能是新闻英语，漏掉了冠词the。例如：

Today, the pace of life is increasing with technological advancements.

当今, 随着科技进步,生活节奏不断增快.

来自《现代汉英综合大词典》

His temperament does not harmonize with a slow, even pace of life. 

他的气质与慢而单调的生活节奏不谐调。

来自辞典例句

As the pace of life continues to increase, we are fast losing the art of relaxation. 

随着生活节奏的不断加快, 我们将很快失去休闲的雅趣。

来自中级百科部分

Ahead, go ahead. Follow the pace of life and proceed. 

“前进,永远前进, 跟随永不停息的生活向前进。 ”

2. 对于大部分状语从句而言，主、从句之间加不加逗号均可，加逗号是为了停顿。尤其句子特长时，说话者需要停顿一下。