原标题：五一抢不到车票，为啥不加开几班夜间高铁？科普中国：夜晚需要对线路进行保养和施工

4月29日，据科普中国报道，每年节假日一开启，火车票几乎是秒光。特别是今年五一，由于旅客出游热情空前高涨，部分热门路线的购票难度不低于春运。不少网友“抱怨”12306APP“开票即候补”。#12306 秒没#冲上热搜，引发广泛关注。

有人不免产生这样的疑问：

为什么普速铁路/高速铁路绝大多数的车次都是在白天，而晚上的班次就那么少呢？不能在晚上加开一些车次，缓解运输压力吗？

这其实还有个类似的问题，就是为什么城市里的地铁到了晚上十一二点就不再运营了呢？

一列复兴号驶出天津动车所。图片来源：中国国家铁路集团有限公司

要回答这个问题，就不得不提到一个比较专业的概念——天窗。这里的“天窗”可不是大家理解的汽车或者建筑顶部的那扇窗户，而是属于轨道交通的专有概念。

根据《铁路营业线施工安全管理办法》第三章中对“天窗”的描述，我们可知如下定义：

“天窗是指列车运行图中不铺画列车运行线或者调整、抽减列车运行线为施工和维修作业预留的时间，按用途分为施工天窗和维修天窗。”

对于任何一种运输工具来说，保养或检修都是非常必要且重要的。

这样一看就比较清楚了，实际上一个非常重要的原因就是在夜晚期间需要对线路进行必要的保养和施工，而这会占用一定的时间。

2019年12月30日实施新运行图。图片来源：央视新闻

比如在线路的某位置由于设计变更增加了几架信号机或几组道岔，对应而来的，就要对车站联锁逻辑进行重新编写，再进行相应的应用软件升级，显然这是一种线路条件的变化。

再比如某线路从某铁路局划转到另外一个铁路局进行管辖，线路的调度管理要由新的调度指挥中心负责，进行重新接入，这显然也要反馈到中心的运行图和大屏变化上，相应地，可能就要对调度集中控制系统（CTC，Centralized Traffic Control System）进行改造。而以上这类工作，显然在白天列车运行的过程中是不允许进行操作的。具体的施工就要等到上边提到的“施工天窗”时间段去进行，而这个时间一般都是在夜晚。

以高速铁路为例，规定要求原则上天窗时间不应小于 240 分钟，但实际上算上施工入场前的准备，施工应急时间预留，以及施工后现场的清理与恢复，一般默认天窗时间都会在凌晨的 00:00-06:00 之间进行。这也就是为什么大家很少会看到 G/D/C 字头的列车在这个时间段内始发的原因。

但好在铁路的线路比较多，两座城市之间的运输线路一般都不会只有一条，所以我们也有机会乘坐如北京-上海 D7 这种“动车卧铺”。夕发朝至，某种意义上满足了一部分经常出差但又苦于赶红眼航班的旅客。

当然，除了主要的线路检修问题限制了轨道交通的夜间运营，客运量也是一个考量因素。

众所周知，无论是地铁还是铁路，作为城市的公共基础设施，是具有一定的公益服务的性质在里面的。这也是大家经常提到，为什么中国的高铁/地铁修完就亏损但还是要修建的一个主要原因。

虽然轨道交通有公益性质，但其背后也承载了许许多多为之付出的工作人员，一味地靠国家补贴显然也不现实，还是要在完成基本任务的基础上去创造利润。而夜间的旅客少、出行密度低，要让铁路车次和白天一样多，会造成大量的资源损耗，所以减少夜间车次也属于可理解的范畴之内。

除此之外，大家都知道，轨道交通行业对于运营工作人员来讲，属于典型的“三班倒”工作制。虽然夜间设备大多是“低效率”运行，但值班人员是必不可少的。夜间是人休息的时候，精神状态也无法与白天相比，如果夜间开行大量的车次，对于工作人员本身也会产生较大的压力。

【来源：科普中国】

责任编辑：刘亚鹏 UN1007

新闻译文：

Original title: May Day cannot get tickets, why not add a few night high-speed trains? Popularization of Science in China: Maintenance and construction of Lines Needed at Night

On April 29th, according to a report from Science Popularization China, train tickets are almost instantly available every holiday. especially this May Day, due to the unprecedented enthusiasm of tourists for travel, the difficulty of purchasing tickets for some popular routes is no less than that of Spring festival travel. Many netizens have complained that the 12306 app is "waiting for invoicing"# 12306 seconds did not # rush to hot search, causing widespread attention.

Some people inevitably have the question:

Why is it that the vast majority of trains on conventional/high-speed railways operate during the day, while there are so few at night? Can't we add more trains at night to alleviate transportation pressure?

There is actually a similar question, which is why the subway in the city no longer operates at 11 or 12 pm?

A Fuxing train departs from Tianjin high-speed train station. image source: China National railway Group Co., Ltd

To answer this question, one must mention a more professional concept - skylight. The "skylight" here is not the window on the top of a car or building that everyone understands, but a proprietary concept of rail transit.

According to the description of "skylight" in Chapter 3 of the "Railway Business Line Construction Safety management Measures", we can define it as follows:

"Skylights refer to the time reserved for construction and maintenance operations in the train operation diagram without drawing train operation lines or adjusting or subtracting train operation lines. They are divided into construction skylights and maintenance skylights according to their purposes."

For any type of transportation, maintenance or repair is very necessary and important.

At first glance, it is quite clear that a very important reason is the need for necessary maintenance and construction of the line during the night, which can take up a certain amount of time.

The new timetable will be implemented on December 30, 2019. Image source: CCTV News

For example, in a certain position of the line, due to design changes, several signal machines or sets of switches have been added. Correspondingly, the station interlocking logic needs to be rewritten and corresponding application software upgrades need to be carried out. Obviously, this is a change in line conditions.

For example, if a certain railway line is transferred from a certain railway bureau to another railway bureau for jurisdiction, the dispatch management of the line needs to be handled by the new dispatch command center for reconnection, which obviously needs to be fed back to the center's operation chart and changes in the large screen. Correspondingly, the CTC (Centralized Traffic Control System) may need to be renovated. And obviously, such work is not allowed to be carried out during the daytime train operation. The specific construction needs to wait until the mentioned "construction skylight" time period, which is usually at night.

Taking high-speed railways as an example, it is required that the skylight time should not be less than 240 minutes in principle. However, in reality, considering the preparation before construction entry, the reserve of construction emergency time, and the cleaning and restoration of the site after construction, the skylight time is generally assumed to be between 00:00 and 06:00 in the morning. That's why it's rare to see trains with the prefix G/D/C departing during this time period.

But fortunately, there are many railway lines, and there is usually not only one transportation line between two cities, so we also have the opportunity to take "high-speed train sleeper" such as the Beijing Shanghai D7. In a sense, arriving late at night satisfies some passengers who frequently travel but struggle to catch red eye flights.

Of course, in addition to the main line maintenance issues that limit the nighttime operation of rail transit, passenger volume is also a consideration factor.

As is well known, whether it is the subway or railway, as the public infrastructure of a city, it has a certain nature of public welfare services. This is also one of the main reasons why China's high-speed rail/subway system still needs to be built despite losing money after being repaired, which is often mentioned.

Although rail transit has a public welfare nature, it also carries many workers who have contributed to it. Relying solely on national subsidies is obviously not realistic, and it is still necessary to create profits on the basis of completing basic tasks. However, with fewer passengers at night and low travel density, it is understandable to reduce the number of railway trains as much as during the day, which will result in significant resource loss.

In addition, as we all know, the rail transit industry belongs to a typical "three shift" work system for operation personnel. Although most night equipment operates at low efficiency, duty personnel are essential. Night is a time for people to rest, and their mental state cannot be compared to that of the day. If a large number of trains are operated at night, it will also create significant pressure on the staff themselves.

【 Source: Science Popularization China 】 Return to Sohu to see more

Editor in charge: Liu Yapeng UN1007

重点词汇

• 火车票 Train tickets ; railway ticket

• 几乎是 Almost ; border on

• 特别是 particular ; special

• 春运 Spring Festival travel rush ; (passenger) transport during the Spring Festival period

• 开票 Invoicing ; make out an invoice ; open the ballot box and count the ballots

• 高速铁路 high-speed railway ; high speed rail ; high-speed rail ; HSR ; TGV

• 绝大多数 most ; vast majority ; overwhelming majority ; solid majority

• 车次 train number ; motor coach number order of departure

• 在白天 in the day ; by day ; in the daytime

• 在晚上 at night ; in the night ; in the evening ; overnight

句子成分分析：

Relying [solely] on national subsidies is [obviously] not realistic, || and it is still necessary to create profits [on the basis 

(of completing basic tasks)].

句子语法结构详解：

* Relying 为动名词，在句中作主语。
* 第1个 is 为系动词作谓语，采用一般现在时。
* realistic 为形容词作表语。
* and 为并列连词，连接并列句。
* it 为先行主语，代表后移的不定式。
* 第2个 is 为系动词作谓语，采用一般现在时。
* necessary 为形容词作表语。
* to create 为不定式。
* completing 为动名词，作介词宾语。
* the 为定冠词。

句子相关词汇解释：

Phrase:

Vocabulary:

句子成分分析：

If a large number of trains are operated [at night], || it will [also] create significant pressure [on the staff themselves].

句子语法结构详解：

* if 为连词，引导条件状语从句。
* operated 为谓语，采用一般现在时和被动语态。
* it 开头为陈述句。
* create 为谓语，采用一般将来时。
* themselves 为同位语
* will 为情态动词。themselves 为自身代词。are 为助动词。the 为定冠词。

句子相关词汇解释：

Phrase:

Vocabulary:

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