Jerzy Linderski, "The Aedileship of Favonius, Curio the Younger and Cicero's Election to the Augurate," Roman Questions: Selected Papers
(Stuttgart: Franz Steiner Verlag, 1995), pp. 231-250 (at 244, n. 54; I removed a period after Riepl):
As illustration, some recorded instances of the speed of travel in republican
times may be adduced. The messenger with the news of the victory at Pydna
covered the distance from Macedonia to Rome in 12 days (Liv. 45.1.11), but
this was an extraordinary feat, and was recorded by Livy as such. For a private
letter a journey of 46 days from Rome to Cilicia (and in the best season of the
year) was regarded by Cicero as a remarkably short time (Cic., Att. 5.19.1),
which is wholly understandable as at the same time a letter from Epirus to
Laodicea in Cilicia traveled (in winter) 48 days (Cic., Att. 6.1.1, 22; cf. L.W.
Hunter, JRS 3  91). A letter sent by Cassius from Syria on 7 May 43
reached Rome some days before the end of June (Cic., Fam. 12.10.1-2; 12.12.5),
rather a good time, especially when taking into account disturbances of the civil
war. In the summer of 47 a freedman of C. Trebonius covered the distance from
Seleucia Pieria (the port of Antioch) to Brundisium in 27 days (Cic., Att.
11.20.1). But this establishes only a general pattern: the speed of any particular
travel depended upon too many unpredictable factors. Cf. W. Riepl, Das
Nachrichtenwesen des Altertums (Leipzig 1913) 205ff; Reineke, RE 16 (1935)
1539-1540. On the speed of sea travel, see the fundamental study of L. Casson,
"Speed under Sail of Ancient Ships," ΤΑΡΑ 82 (1951) 136-148.