As-salamu'aleikum,
It sometimes happens that I'm stuck in traffic at the time of maghrib, which means I can find no way to pray on time. This frustrates me. Alhamdulillah this does not happen often since I always try to finish my work before this time so that I will be at home when the call for prayer is called. However, what should I do when I am in this situation and how sinful am I because of it?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

If a person is stuck in traffic and he/she is not able to come out of it [the traffic] and perform the prayer at its prescribed fixed time, then we hope that he/she is not sinful as Allaah Says (what means): {No person is charged with more than his capacity.}[Quran 2:233] However, if one knows that the traffic jam will not end before the time of ‘Ishaa’ and he/she will not be able to perform the Maghrib prayer at its prescribed fixed time, then he/she should intend to combine the Maghrib prayer with the ‘Ishaa’ prayer at the time of ‘Ishaa’ prayer. Indeed, it is confirmed that the Prophet combined the prayer in Al-Madeenah while there was no rain and he was not on a journey, and he did so just in order not to burden his nation.

For more benefit, please refer to Fatwa 85790.

Allaah Knows best.