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Entering from Pakistan:
As of the time of writing, the Khyber Pass is closed for entry to Afghanistan.
That means you from Peshawar cannot catch a taxi, a bus, a moto-rickshaw, hitch-hike, walk, drive your car, your bus, ride your motorbike, scooter, push-bike, unicycle, pony, donkey, whatever to the Torkham border and on to the Jalalabad-Kabul road until further notice.
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Entering from Iran:
From Mashad there are usually a handful of busses, mostly carrying freight to Herat. Make sure you book you tickets at least the day before you intend to depart, as the busses leave around 04:00 to 07:00 in the morning.
Expect to be sitting next to boxes of tiles, panes of glass, artificial flowers, kid's bath toys and all sorts of other random crap that there is apparently an urgent need for in western Afghanistan.
(to be continued)