A bus user said passengers have been left stranded because buses are full, running late and confusion at stops means drivers are not stopping to pick people up.
Nelly Adamo said people struggling to get on full buses were left frustrated when they could see buses with room not bothering to stop behind to pick up.
Stagecoach has blamed delays on the roadworks near the University of Warwick - saying the congestion was so bad that roads leaving the campus were closed twice to enable Gibbet Hill Road traffic to clear.
Nelly, aged 18, of Whitnash, is a fresher at the university and bought a three-term pass costing nearly £300 for the U1 bus service between Sydenham, Leamington and the campus.
She said: “Stagecoach wants the money up front saying there’s a bus up to every ten minutes.
“At the university I’ve been left waiting more than an hour for a bus. Some don’t stop because they are so full and some don’t stop because they have a ‘Not in Service’ sign on.
“Buses are so full that people are standing at the front and pushed against the door.”
Nelly, who is on an Hispanic and Italian studies course, said her parents in Whitnash have had drive over to get her home because she can’t get on buses.
She said her mother Sarah has complained to Stagecoach, and said customer services staff told her they “had been swamped” with complaints.
“The bus drivers should pay more attention at the bus stops when people are struggling to get on a bus that’s already crowded. Why do they sail past when it’s obvious people are waiting to get a bus?
“People should complain to Stagecoach. The more who complain, the quicker Stagecoach will do something,” said Nelly, who went to Trinity Catholic School.
Chris Child, marketing manager at Stagecoach Midlands, said staff had been put on the campus in an effort to ease the problems and extra buses laid on to fill the gaps in the service.
And he added: “Stagecoach U1 service has been badly affected by the roadworks, particularly since the latest phase of works has changed from two-way lights to four-ways lights.
“Buses have experienced delays of up to 40 minutes getting through these roadworks, particularly during the afternoon.
“In addition, on Monday and Tuesday of last week the roads leaving the university site were closed for 15 minutes to release the traffic outside the campus.
“The company is in discussions about introducing an alternative route with the university if these roadworks/traffic light arrangements continue unchanged.”