Are not two men entering upon a woman considered ikhtilat (impermissible mixing)? What is the difference between them? Does khalwa (impermissible private seclusion) cease to exist if there is more than one woman with the driver, and what is the evidence for that? What are the conditions for mahramiyyah shar'iyyah (legitimate state of being a mahram) for travel? Is it permissible to speak with a non-mahram woman if she is fully veiled, instead of speaking from behind a physical barrier?

1- The hadith referred to by the questioner was narrated by Muslim from Abdullah ibn Amr ibn al-Aas (may Allah be pleased with them both), and its text states that the Prophet (peace be upon him) said: "No man shall enter upon a woman whose husband is absent unless there are one or two men with him." The interpretation of this hadith is that the permissibility of a man, or two or three men, being alone with a foreign woman is not absolute. It is forbidden according to the scholars of the Madhhabs, unless the temptation (fitna) is secured by the presence of a group of people from whom immorality is unlikely to occur due to their righteousness or chivalry. The blameworthy mixing is that which involves a gathering between foreign men and women without necessity, or that which involves a soft voice or the uncovering of 'awrah (intimate parts).

2- Scholars have differed regarding the absence of seclusion when two or more women are present with a man. The permissibility revolves around the security from temptation (fitna). Whenever temptation is feared, the presence of men with women becomes forbidden.

3- The Prophet (peace be upon him) forbade a woman from traveling without a mahram. A mahram is someone with whom marriage is permanently forbidden, not due to a temporary forbidden cause. The mahram relations are mentioned in the Qur'an and Sunnah. Examples include His (Allah's) saying: "Forbidden to you are your mothers and your daughters and your sisters and your paternal aunts and your maternal aunts and the daughters of a brother and the daughters of a sister and your mothers who have suckled you and your sisters through suckling and the mothers of your wives and your stepdaughters who are under your guardianship [born] of your wives unto whom you have gone in. But if you have not gone in unto them, there is no sin upon you. And [forbidden are] the wives of your sons who are from your [own] loins..." [An-Nisa: 23].

4- Whenever temptation (fitna) is feared, seclusion is forbidden, even among mahrams themselves.