Following claims Chris Froome had urine thrown in his face, Tour de France bosses have called for riders to be respected.
Tour de France spectators have been asked to respect the peloton as the race enters its closing stages.
General classification leader Chris Froome - blighted by allegations of doping during this year's Tour - claimed to have had urine thrown in his face during stage 14, with Team Sky boss Dave Brailsford later labelling the crowd as "out of control".
Australian rider Richie Porte said he was punched during stage 10 of a race in which fans have turned on Team Sky.
And the Union Cycliste Internationale (UCI), along with organisers the Amaury Sport Organisation (ASO), has now taken measures to stave off similar incidents in the final four days of action.
A joint statement read: "The peloton of the 102nd edition of the Tour de France enters a decisive phase of the race as it enters the Alps, where the riders require optimal conditions in order to perform to their best before arriving in Paris on Sunday.
"UCI President Brian Cookson and Tour de France Director Christian Prudhomme ask crowds along the roadside to respect every rider, and the integrity of the riders and in particular the Yellow Jersey.
"The UCI and ASO publicly regretted the aggressions suffered by the leader of the overall classification from some spectators during the 14th stage between Rodez and Mende, while at the same time thanking the large majority of the public which respects the athletes."
Froome held a lead of three minutes and 10 seconds over Movistar rider Nairo Quintana ahead of stage 18 on Thursday.