Passengers are being reminded that the frequency of buses running through Oxford is to be reduced to cope with congestion.

Bus company bosses say timetables for key co-ordinated bus routes will be revised from today to 'improve reliability'.

Changes will be made to a number of city routes to cope with worsening traffic congestion in Oxford.

Oxford Bus Company and Stagecoach have worked together to adjust timetables and they called on local authorities for more support 'to keep Oxford moving'.

Roadworks have cause major delays in Botley Road, Frideswide Square and during the Access to Headington project.

Oxford Bus Company managing Director Phil Southall said: “Congestion has worsened in the city and therefore we have had to make changes to the way we operate on some of our key city services.

"The same number of vehicles will be in operation, but the frequency will be reduced.

"This will improve overall reliability for passengers.

“The number of temporary traffic lights and roadworks in the city has had a negative impact on public transport.

"In the long-term we will need improved support from the local authorities to keep Oxford moving.”

Hugh Jaeger, a spokesman for the Oxford branch of Bus Users UK, said: "Key routes are affected, with 1 and 5 serving Cowley and Blackbird Leys, and the 8 and 9 going to Headington.

"In my view the two bus operators have been forced into this by the county council's traffic management.

"Reducing the frequency of these key services will make the buses more crowded, particularly at peak times, but the bus companies have no option."

Mr Jaeger said St Aldate's and the west end of High Street were major pinch points after the county council forced so many buses out of Queen Street.

He added: "There are now too many in St Aldate's."

Mr Jaeger said last year new paving next to the bus stop outside Lincoln College library in High Street was widened by two metres, causing a bottleneck.

He added: "The council will have to rip it up and start again because everything at this point is grinding to a halt."

Martin Sutton, Stagecoach’s Managing Director, said: “Traffic patterns are continually changing and monitoring of our automatic vehicle location systems indicates that minor adjustments are necessary on some of the busiest city routes.

"These housekeeping measures should result in an improved service for our customers.”

Minor adjustments will be made to service frequencies at the busiest times of day to 'provide improved reliability', according to the bus companies.

Timetables adjustments will be introduced on services 1, 3A, 5, 8 and 9 from April 8.

The 3A service will be re-timed and operate via the Sadler Building in the Oxford Science Park.

During the afternoon and early evening, the frequency will be reduced to allow an increase in running time and improved reliability.

On Saturday late afternoons and early evenings, the Kassam Stadium service will also be adjusted to improve reliability.

Running time for the city5 and Stagecoach 1 service will be adjusted to provide more boarding time at the busy St Aldate’s stop.

Journeys will also depart earlier from Oxford rail station during off-peak hours between Monday and Friday to ease bus congestion on the station forecourt.

Increased running time will be introduced to the City8 and city9 services to improve reliability.

Minor adjustments to improve punctuality are also being made to Stagecoach’s service 10 during the busy afternoon period.

Oxfordshire County Council, the highways authority, has said it will continue to work closely with the bus companies.