It says helmet use is also falling among cyclists and e-scooter users.
Just one in five cyclists wear hi-visibility clothing.
That's according to the RSA, who observed about two thousand road users in August.
They say helmet use is also falling among cyclists and e-scooter users.
RSA spokesperson David Martin said people not wearing helmets while on e-scooters is particularly worrying.

Kfm Obituary Notices
Naas Crossing Project Delayed Despite €50,000 Funding
Kildare Gardaí See Increase In Drivers Taking Off Without Paying For Fuel, Whilst State Of The Nation Address Not Ruled Out By Taoiseach
Gardaí Warn People To Be "Buyer" And "Seller" Aware After Kilcullen Incident
Kildare Sees 45 Per Cent Increase In Electric Car Vehicles In First Three Months Of 2026
"When I Look Back At It, I Had All The Symptoms": Kildare Resident On His Diagnosis, As April Marks Bowel Cancer Awareness Month
Warning Over Long Waits At Naas Emergency Department
Calls For Reform After Garda Convicted Over Scrambler Pursuit