Each day in the United States, approximately 9 people are killed and more than 1,000 injured in crashes that are reported to involve a distracted driver. 1 Distracted driving is driving while doing another activity that takes your attention away from driving.
This is called the post-void residual. The bladder has a approximately 500ml capacity. You should feel a desire to void at ~250ml. Urinary retention is measured by using a special type of ultrasound (bladder scan), or by inserting a bladder catheter and measuring how much urine comes out. I'm a 4th year US med student. On one of my urology rotation I asked the Sr. resident this exact question.
In essence, you can be in control of your bladder, rather than your bladder habitually controlling your life. A normal fluid intake is between 1500-2000 cc's (50-70 oz.) per day, which should produce 1200-1500 cc's (40-50 oz.) of urine output. The normal bladder capacity before you feel any sensation of urge is about 300 cc's (10 oz.). Normal voiding volumes are 210-300 cc's (7-10 oz.) with the first morning voiding usually being the largest at 400-500 cc's.