Why Is My Three Year Old Still Peeing Her Pants

Why is my three year old still peeing her pants and what can I do about it? She's been potty trained for a year now and has been having up to four accidents a day since she's been potty trained. I don't just ask and give her the option to go. If it's been longer than an hour, I make her go. It's a fight every time. She denies having to go, but goes every time I make her. I have been fighting the urge to just put her back in pull ups, but that would reverse everything I've worked for a year to do. I can't take her anywhere and we're planning a road trip next week and I'm absolutely dreading it. I am losing my mind and my patience. I have done the potty charts with rewards, constant verbal praise, books on going potty and bribery. Literally nothing works with her. She's a very difficult child to being with, which makes all this that much harder.