The incident occurred around 5:45 p.m. on the Via de la Valle on-ramp to northbound Interstate 5.
The woman was transported to Scripps Memorial Hospital with life-threatening injuries. The dog the woman was walking was taken to a local animal hospital. There was no information on the condition of the dog.
While the cause of the crash was still being investigated, area residents said the sun at that time may have impaired the driver's vision.
"I usually drive that route when I go surfing at sunset, so it's not surprising. I usually have trouble [seeing] myself driving down that road with that glare," Solana Beach resident Nick Szyndlar said.