The cooling system is pressurized so the coolant would come out as you describe when the radiator cap is removed with the engine hot. Based on your description it dosn't sound like you have a problem with your vehicle if it's not overheating with the gauge nearing the red. If you believe there is a problem check if the cooling fan is coming on at each speed.
it's important to know if you are in stop and go traffic or on the highway when this occurs.You should make sure you have heat a the vents in the cabin and make sure both fans are cycling.no heat would mean coolant loss no fans would make the car run hot too.If the fans are cycling and you have heat it is possible to have a partially blocked radiator or a T-stat problem.Generally if it takes an hour to overheat in traffic its due to blockage.the other potential problems are temp sensor or even the gauge in the instrument cluster
If I'm not mistaken , the rad. cap specifically warns not to open when hot , for a reason. Temp guage in middle is about 210F. Scalding to us is 140F. So aside from taking the cap off under not-so-good conditions , what's the problem?