Climate activists have begun a week-long street blockade – prompting a police force to use emergency powers to shut off roads.
Members of Extinction Rebellion claim they had sent warnings to Cambridge University, and the city and county councils, to meet a series of demands.
It comes two days after a meeting had to be abandoned when a protester abseiled into the council chamber.
A spokeswoman said the blockade would remain in place until 23 February.
The group says it wants the university to “cut ties” with fossil fuel companies, and is calling for a “citizen’s assembly on climate justice” to be established in Cambridge.
It also wants the city’s public transport system to be more reliant on green energy.
Activists have set up a camp on Trumpington Road, blocking entry to the city from Fen Causeway during the half-term week.
Police have created diversions for traffic and public transport accessing the city centre, with a number of bus stops suspended.
A University of Cambridge spokeswoman said hundreds of its researchers “are working hard to develop real solutions to the climate emergency every day”.
“The university respects the right to protest and free speech, and demonstrates its commitment to serve society by making ground-breaking discoveries and developing ideas that will support the rapid decarbonisation of the global economy in a way that is practical, ethical and equitable,” she added.
In November, the university launched Cambridge Zero, led by Dr Emily Shuckburgh, one of the UK’s leading climate scientists.
Activist Amelia Halls, 21, said: “On 1 January we issued three demands of the institutions.
“We acknowledge that we are causing a disruption – but it’s not enough to plant a load of trees and say by a certain time we’ll be carbon neutral – it’s not soon enough.”
Supt James Sutherland, of Cambridgeshire Police, said: “We review all reports of protest both spontaneous and planned.
“We have to strike a balance between the need to allow peaceful protest within the city and the disruption that the protest itself causes.”