Bukhari

Hadith Commentary:
Most scholars have considered traveling alone to be disliked (makruh).
Because it is mentioned in the hadith that a lone traveler is a devil, and two are two devils, and three are a group.
The purpose of Imam Bukhari rahimahullah in bringing this chapter is to show that, in cases of necessity—such as for reconnaissance or similar needs—traveling alone is permissible.
Some have said that if there is no fear on the way, then there is no objection to traveling alone, and the hadith prohibiting it is to be understood as applying when there is fear.
(Wahidi)
Even nowadays, if journeys by train, car, or airplane are undertaken in the form of a group, there are many benefits in this which are not found in a state of solitude.
Being alone during travel is, in reality, a cause of great hardship, even if the journey is by train, car, or airplane.

Hadith Commentary:
➊
Imam Bukhari rahimahullah has kept the chapter title ambiguous.
He has not explicitly stated whether it is permissible or impermissible.
In reality, there are two possible situations regarding traveling at night.
One situation is that of safety and security.
In such a journey, it is predominantly assumed that the enemy will not be able to cause any harm.
In this case, traveling alone is permissible, as is evident from the hadith of Zubair radi Allahu anhu.
The second situation is one of fear and apprehension.
In this case, one should avoid traveling alone, as is understood from the hadith narrated from Abdullah bin Umar radi Allahu anhu.
➋
The commentator of Bukhari, Ibn Munir rahimahullah, states that for the benefit of warfare, traveling alone is permissible, such as to gather intelligence about the enemy, conduct espionage, or to make military arrangements. In such circumstances, traveling alone at night is permissible. Apart from these, traveling alone is not free from harm.
(Fath al-Bari: 6/167)

Explanation:
1:
If the circumstances are such that the roads are unsafe and there is danger to life and property, then in such a situation, traveling alone without necessity is prohibited. However, if there is some compulsion, then there is no harm. The Prophet (sallallahu alayhi wa sallam) sent some companions (radi Allahu anhum) on solitary journeys when there was a need.

Benefits and Issues:

➊
During a long journey, situations may often arise where one needs cooperation and assistance from a companion; therefore, on a journey, one should have the company of a righteous travel companion.

➋
There are more dangers at night, so it is necessary to avoid traveling alone at night.

➌
If there is an extreme necessity, then traveling alone is permissible, as Abu Dharr (radi Allahu anhu) undertook the journey of migration alone.

➍
Going from one place to another within a populated area is not commonly considered a journey; in such cases, solitude is permissible.

Benefit:
Traveling alone at night is disliked (makruh), as Imam Tirmidhi rahimahullah has established a chapter on this hadith. However, in case of necessity or during times of war, traveling alone is permissible. [صحيح البخاري : 2997]