Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
It is permissible for a traveling person to combine two Prayers. One may combine Zhuhr and `Asr together and Maghrib and `Isha’ together, either by offering the second at the time of the first or by delaying the first to the time of the second.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you are traveling 80 miles each way, you definitely fall under the category of a musafir (traveler); and therefore you are allowed to combine Maghrib and `Isha’ as well as between Zhuhr and `Asr while you are still traveling.
During the journey you are allowed to combine certain Prayers either by advancing them or postponing them: For example, you may postpone Maghrib to the time of `Isha’ or advance `Isha’ to the time of Maghrib.
In your case, while commuting, you can make the intention of doing Maghrib with `Isha’ when you reach home.
I must, however, caution you that you are not allowed to pray Fajr with Zhuhr, `Asr with Magrib, or `Isha’ with Fajr since the permissibility of Jam` (combining prayers) is only applicable to Zhuhr and `Asr, and Maghrib and `Isha’.
The ruling that a traveler can combine the prayers has been the authentic view of the vast majority of scholars and imams; it is based on the authentic practices of the Prophet (peace and blessings be upon him), his companions and the pious predecessors (As-Salaf As-Salih).
Almighty Allah knows best.
Excerpted, with slight modifications, from: www.islam.ca