Regulatory Signs: What You Must Do
Regulatory signs are the white rectangles with black legends (plus red for prohibitions) that tell you what the law requires you to do - or not do. The Illinois exam tests whether you can read the legend, match it to the correct driving action, and recognize the state's default numbers where no sign is posted.
Reading the sign correctly
- White background, black message: a rule you must obey, such as STOP HERE ON RED, KEEP RIGHT, or LEFT TURN ONLY.
- A red circle with a diagonal slash means the maneuver pictured is prohibited; a red legend such as NO PARKING means the same thing in words.
- A small plaque under the main sign changes the rule - EXCEPT RIGHT TURN, 7 AM–9 AM, TRUCKS ONLY. The plaque, not the main sign, controls.
- Unless a sign says otherwise, Illinois allows a right turn on red after a full stop, and a left turn on red from a one-way street onto another one-way street.
- Where nothing is posted, Illinois defaults include 30 mph in an urban district and 55 mph on rural highways outside urban districts.
Worked example
You approach a white sign showing a black right-turn arrow inside a red circle and slash, with a plaque reading 4 PM–6 PM. The slash means right turns are prohibited, and the plaque limits the ban to those hours. Outside 4–6 PM you may turn right after stopping, provided no other sign forbids it. Reading only NO RIGHT TURN and skipping the plaque would make you detour needlessly.
Traps that cost marks
- Treating a white regulatory sign as advisory: a violation is a moving violation, not a suggestion.
- Missing the exception plaque, or applying an exception to the wrong hours.
- Assuming right-on-red is always legal - it is not where a sign prohibits it or where you would cross a pedestrian signal.
- Confusing default speed limits with posted ones.