The bomb was planted on Musharraf's route from an army hospital in Rawalpindi where he has been staying since January to his home on the outskirts of Islamabad and went off at around 2:00 am (2100 GMT Wednesday).
Nobody was injured and there have so far been no claims of responsibility.
"Four kilograms of explosive device planted in a pipeline under a bridge exploded around 20 minutes before the former president was supposed to cross the spot," senior police official Liaqat Niazi said.
The blast occurred at the Faizabad interchange, which lies at the boundary of the two cities, and destroyed a footpath around two meters wide.
Niazi said the former president was then taken home via an alternative route.
Muhammad Naeem, a spokesman for the Islamabad police, confirmed the incident, saying a bomb disposal squad had cordoned off the area after the blast and searched for additional explosives.
"Nobody was injured in the blast," he said, adding Musharraf was the intended target.
Musharraf, who led Pakistan from 1999 to 2008, returned from self-imposed exile in March last year to fight in general elections, but was barred from taking part and has faced a series of legal cases including treason.
The Taliban also vowed to send a squad of suicide bombers to kill him, and security threats have prevented him from appearing at all but two of his hearings.
It was the fourth attempt on his life, with the first three occurring while he was in office.
NJF/NJF