Solid Yellow Center Line, Fog, and a Bridge Object Marker
You are driving a loaded pickup at night in dense fog on a two-lane Montana highway. The center line is a solid yellow line on your side paired with a broken yellow line on the opposite side. The right edge line is white. Ahead, a slow-moving flatbed truck with a flashing amber light is traveling at 20 mph. You have followed it for a mile. The fog limits visibility to about 150 feet. You see a gap in oncoming traffic and consider passing. Just before the truck, the broken yellow line on your side changes to solid yellow, and a yellow object marker with a diagonal stripe appears on the right shoulder near a bridge abutment. The road curves left after the bridge. Your passenger says the broken line means passing is allowed and the gap is enough.
1. What does the center-line pattern mean for your direction, and does the broken yellow line on the opposite side authorize you to pass?
Read the worked answer
The solid yellow line on your side means passing is prohibited for your direction. The broken yellow line on the opposite side applies to oncoming traffic and allows those drivers to pass when safe; it does not authorize you to use their lane. Your passenger is misreading which side of the center line controls your movement. You must wait until your side has a broken yellow line, and even then passing must be safe and legal. With fog, a bridge, and a curve ahead, the marking prohibition and the safety analysis both point to staying behind the truck.
2. What does the yellow object marker with a diagonal stripe at the bridge abutment indicate?
Read the worked answer
The yellow object marker warns of an obstruction close to the roadway, such as a bridge abutment or a narrowed shoulder. The diagonal stripe is oriented to show the side on which traffic should pass, so it reinforces that the hazard is at the right edge and that you should not drift toward it. It is not a passing-zone marker and does not mean the shoulder is a safe refuge. In fog, the marker is telling you that the right-side margin is shrinking just as you approach a bridge and a curve. Keep your lane position centered and reduce speed rather than swinging left to pass.
3. Given 150 feet of visibility, the bridge, and the curve, should you pass if the oncoming gap looks clear? Explain.
Read the worked answer
No. A passing maneuver at highway speed takes several seconds and requires far more clear sight distance than 150 feet. Even if the oncoming gap looks empty, the fog and the left curve can hide a vehicle until it is too close to react. The solid yellow line on your side independently prohibits passing. The bridge abutment and object marker narrow your escape path on the right, and the flatbed's flashing amber light warns that it is a slow vehicle. Slow to a safe speed, increase following distance, use low-beam headlights or fog lights, and wait for a legal passing zone with enough visibility. If the fog becomes too thick to see a safe path, pull off at a safe location rather than forcing a pass.