Accident on busway - diversion via A14

A friend told me he'd been on a busway bus on Saturday that had been diverted onto the A14 because of an incident.

All is revealed in today's Hunts Post ( 5 October, page1). There was a cyclist on the bus tracks and he didn't respond to the bus sounding its horn repeatedly. The cyclist had headphones on and therefore couldn't hear the bus. Fortunately he managed to dive off his bike just in time, but the bus ran over the bike crushing it to bits. The bus was damaged too and had to be taken out of service.

A passenger on the bus said 'For a good mile the driver was beeping her horn'. That implies the driver saw the cyclist from some distance away. If that was the case, why did she not slow her bus right down, so as to be able to stop before hitting the bike?