The students would emerge on their bikes, in the tens of thousands, seemingly out of nowhere. Like a flash mob on wheels, they rode for hours in the night, by the light of streetlamps, sometimes bursting into verses of the Chinese national anthem. Some carried Chinese flags.

成千上万的学生骑着自行车出现，似乎不知从哪里冒出来的。他们就像一群带着轮子的快闪族，在夜晚的路灯下连续骑行数小时，有时还会突然唱起中国国歌。一些人举着中国国旗。

They were making the 40-mile journey from the Chinese city of Zhengzhou, the capital of Henan Province, to the neighboring city of Kaifeng, a cycling trip that can take up to five hours one-way. Why? For the sake of it.

他们从中国河南省会郑州出发，骑行约60公里，前往邻近的城市开封，单程可能需要五个小时。为什么？不为什么。

It isn’t clear when the craze really took off, but by early this month, it was drawing hundreds of riders seemingly every night. At first it had been celebrated online and even by the People’s Daily, the Communist Party mouthpiece, which described the night rides as “a symbol of youthful energy and the joy of shared experiences.”

目前还不清楚这股热潮是什么时候开始兴起的，但到本月初，似乎每晚都有数百名骑行者加入。起初，在网上，甚至共产党的喉舌《人民日报》都对这股热潮表示赞许，称夜骑是“青春的象征和分享的快乐”。

But over the weekend, after the number of riders swelled to the tens of thousands in a country where officials are increasingly wary of impromptu crowds, local authorities shut it down, citing traffic and safety concerns.

但到了周末，骑行者激增至数万人之后，地方当局以交通和安全方面的担忧为由叫停了这项活动。在这个国家，官员们对临时聚集的人群越来越警惕。

The nighttime escapades started in June when four college friends in Zhengzhou decided to bike to Kaifeng to eat a type of soup dumpling that is the city’s specialty, Chinese news media has reported. Soon, hordes of college students were making the trip, too, helped by easy access to shared bicycles that are cheap and ubiquitous in many Chinese cities.

据中国新闻媒体报道，这种夜间冒险始于今年6月，当时郑州四个大学生朋友决定骑车去开封吃开封特产灌汤包。很快，大批大学生加入了这一行列，因为在中国许多城市，共享单车既便宜又随处可见。

The students, seemingly attracted by a sense of spontaneity and adventure, posted photos and videos of their own journeys online with the caption: “Youth has no price tag.”

学生们似乎被一种自发性和冒险精神所吸引，他们在网上发布行程照片和视频，并配文：“青春没有售价。”

The buzz around the night rides drew Bin Li, a third-year engineering student at a university in Henan who boarded a train to Zhengzhou on Thursday with nothing but the clothes he was wearing.

夜间的喧闹吸引了河南一所大学工程系三年级学生李斌（音）。周四，除了身上的衣服他什么都没带，就这样登上了开往郑州的火车。

His leap of faith paid off. Everything he needed — water, food, a bike and even companionship — materialized along the route. At the starting point, he met another college student. They set out just before midnight, and the two strangers became impromptu riding partners for the five-hour journey that followed.

他的大胆尝试得到了回报。他所需要的一切——水、食物、自行车，甚至陪伴——都在沿途得到了。在起点，他遇到了另一个大学生。他们在午夜之前出发，在接下来的五个小时的旅程中，这两个陌生人成了临时的骑行伙伴。

“It didn’t feel that long because I was talking with all these strangers we met along the way,” he said. “When so many people came together to do something as one, there was a real sense of community.”

“我感觉时间并不长，因为我一直在和一路上遇到的陌生人聊天，”他说。“这么多人聚在一起做一件事的时候，就会有一种真正的集体感。”

The night unfolded like a rolling street festival, with cars in adjacent lanes occasionally slowing down to blast music for the riders. Some people even set off fireworks along the route. At one point, a rider appeared with a national flag strapped to his back, spontaneously prompting the crowd to break into the national anthem, “March of the Volunteers.”

这个夜晚就像是不断滚动的街头节日，相邻车道上的汽车偶尔会放慢速度，为骑行者播放轰鸣的音乐。一些人甚至在沿途燃放烟花。有一次，一名背上系着国旗的骑手出现了，人群不由自主地唱起了国歌《义勇军进行曲》。

“You could hear how exhausted people were, but they were still trying their best to sing,” Mr. Li said. “With the national flag waving in front and everyone singing the anthem behind it, there was this really powerful energy, truly incredible.”

“你可以听到人们有多疲惫，但他们仍然努力唱歌，”李斌说。“国旗在前面挥舞，大家都跟在后面唱国歌，这种能量真的很强大，真的很不可思议。”

Mr. Li arrived in Kaifeng around 4 a.m. on Friday and followed the crowd to a Song dynasty theme park. The bike Mr. Li rented for the journey cost him 26 yuan, or about $4.

李斌于周五凌晨4点左右抵达开封，跟随人群前往一个宋代文化主题公园。李斌租自行车花了他26元（约合四美元）。

At first, officials had encouraged the craze, which was seen as good for business and tourism. The theme park in Kaifeng, along with many other popular tourist attractions, changed their schedules to open early and offered free admissions to students. Volunteers distributed free breakfast at the gate.

起初，官员们鼓励这种热潮，认为这有利于商业和旅游业。开封的主题公园和许多受欢迎的旅游景点对开放时间做出了调整，提前开放，让学生免费入场。志愿者在门口分发免费早餐。

The city also set up additional bike docking sites, and traffic police were dispatched to escort the students on their journeys. Many students would spend a day or two in Kaifeng, then take the train back, state media has reported.

开封市还设立了额外的自行车停靠点，并派遣交警护送学生。据官方媒体报道，许多学生会在开封待上一两天，然后坐火车回去。

But the welcome quickly turned into criticism.

但欢迎很快变成了批评。

On Friday night, photos and videos showed bikes filling up a multilane road between the two cities, with cars squeezed to the sides and the crowd stretching for miles. By then, the trend had spread beyond college students, drawing participants of all ages from cities across the country.

周五晚上，照片和视频显示，两座城市之间的一条多车道公路上挤满了自行车，汽车被挤到两边，人群绵延数公里。当时，这一趋势已经蔓延到大学生之外，吸引了来自全国各个城市各个年龄段的参与者。

Among them was Fen Shen, a 32-year-old construction contractor in Zhengzhou. Watching the youthful energy sweep through his city, he felt an urge to help even if he did not want to bike himself.

32岁的郑州市建筑承包商沈芬（音）就是其中之一。看着这股年轻的活力席卷他的城市，即使他自己不想骑车，也有一种想帮忙的冲动。。

“I felt inspired by the atmosphere,” Mr. Shen said. “It’s just so good to be young — there’s no pressure, you can just pick up and go whenever you feel like it.”

“我被这里的氛围鼓舞了，”沈芬说。“年轻真是太好了——没有压力，你可以随时拿起东西就走。”

骑车的人群常常绵延数公里。当局起初鼓励这股热潮，认为这有利于经济。

He joined online groups to coordinate rides and help out-of-towners locate available bikes for rent around the city. But his participation was short-lived. By Friday night, many would-be riders gave up after finding that rental bikes were already taken.

他加入了在线群组，协调骑行活动，帮助外地人在城市内找到可供出租的自行车。但他的参与很短暂。到周五晚上，许多想骑行的人发现租赁的自行车已被租用，于是放弃了。

The next day, both cities announced that on Saturday night, they would close the lanes for nonmotorized vehicles — that is, bikes — on the road the students had been using. Some bike rental companies that operate in Zhengzhou announced that their bikes would lock if residents attempted to take them out a designated zone within the city.

第二天，两个城市都宣布，将在周六晚上关闭学生们一直使用的道路上的非机动车道，也就是自行车道。在郑州运营的一些自行车租赁公司宣布，如果居民试图将自行车带出城市内的指定区域，他们的自行车将被锁定。

When Mr. Shen went to the usual starting point on Saturday, the scene had changed. Police officers and security guards were stationed at several intersections, blocking access to the highway, he said.

周六，当沈芬回到平时的出发点时，一切都变了。他说，警察和保安人员驻扎在几个路口，封锁了通往高速公路的通道。

“While the youth were carousing, more and more people were beginning to worry about the hidden dangers of the large gathering of bikes,” the Kaifeng Public Security Bureau said in a social media post on Saturday.

“青春尽显狂欢的同时，越来越多的人开始担心扎堆骑行的安全隐患，”开封市公安局周六在社交媒体上发帖称。

What if an ambulance needed to use the road but couldn’t get through, the post asked, or what if a bicyclist in the crowd fell but was unable to escape the congestion?

帖子问道，如果救护车需要通过这条路，但无法通过，或者如果人群中的骑行者摔倒了，但无法逃离拥堵，怎么办？

“You don’t need to bike in a large group or late at night,” the bureau added. “Why not set off during the day?”

“骑行不必扎堆，也不必深夜，”该局补充说。“何不白天出发？”

The change in tone reflects the delicate balance Chinese authorities face when managing spontaneous youth movements, said Dali Yang, a professor at the University of Chicago who studies Chinese politics.

芝加哥大学研究中国政治的教授杨大利（音）说，语气的变化反映了中国当局在管理自发的青年运动时面临的微妙平衡。

On one hand, officials saw the students’ enthusiasm as a way to drive broader excitement about a smaller city like Kaifeng. But they may have underestimated the pent-up energy of young people, Mr. Yang said, including students from other parts of the country, at a time when many are still carrying the emotional weight of the pandemic, when college campuses were locked down.

一方面，官员们把学生们的热情视为一种可以激发人们对开封这样一个小城市更广泛兴趣的方式。但是，杨大利说，他们可能低估了年轻人被压抑的能量，包括来自全国其他地区的学生，此时许多人还在承受着疫情期间大学校园被封锁时带来的情绪负担。

“Instead of trying to find a way to channel the students’ energy, the stability-obsessed authorities simply decided the easiest way is to limit their access and mobility,” he said.

“执迷于稳定的当局没有设法疏导学生的精力，而是简单地决定，最方便的方法就是限制他们的进入和流动，”他说。

Mr. Li, the engineering student, said his university is now warning students not to join the night rides.

工科学生李斌说，他所在的大学现在警告学生不要参加夜骑活动。

“These are the only years in my life where I don’t have to worry about other things, so I have to make memories that will last,” he said. “Once I start working, there will no longer be a chance to do this.”

“这是我一生中唯一不用为其他事情操心的日子，所以必须留下永久的回忆，”他说。“一旦开始工作，就再也没有机会了。”

On Chinese social media, people posted messages saying that their universities in Henan were restricting students from leaving campus without permission, but the measures could not immediately be verified.

在中国的社交媒体上，人们发布消息称，河南的大学限制学生擅自离开校园，但这些措施无法立即得到证实。

Some also posted messages and videos saying that the restrictions would not stop them — instead of riding, they would simply walk.

一些人还发布消息和视频称，这些限制不会阻止他们——不骑车，他们可以直接步行。