Title: Yellow
Content:  Yellow is the most visible color from a distance, so it is often used for objects that need to be seen, such as fire engines, road maintenance equipment, school buses and taxicabs. It is also often used for warning signs, since yellow traditionally signals caution, rather than danger. Safety yellow is often used for safety and accident prevention information. A yellow light on a traffic signal means slow down, but not stop. The Occupational Safety and Health Administration (OSHA) uses Pantone 116 (a yellow hue) as their standard color implying "general warning," while the Federal Highway Administration similarly uses yellow to communicate warning or caution on highway signage. A yellow penalty card in a soccer match means warning, but not expulsion.
Title: Radar speed sign
Content:  XX (MPH) or such similar legend should be shown. The color of the changeable message legend should be a yellow legend on a black background or the reverse of these colors.” The first paragraph allows for the use of VSL Signs (Variable Speed Limit signs), the second for use of a Speed Feedback Sign. The third is “Guidance”, not regulation, concerning the content and color of the “legend”, typically the static signage surrounding the electronic display. Two other states have been much more specific in their directive regarding Speed Feedback Signs, California and Minnesota. California’s most recent comments were somewhat more specific as to 
Title: Driving in the United States
Content:  To convey the message immediately, the roadway signs in the US use symbols rather than words. The use of symbols is not bothered by any language barriers, and can be instant communication for drivers and pedestrians in order to manage the transportation and the traffic safety. According to Federal Highway Administration, it states “the color of roadway signs is an important indicator of the information they contain. The use of red on signs is limited to stop, yield, and prohibition signs. A white background indicates a regulatory sign; yellow conveys a general warning message; green shows permitted traffic movements or directional guidance; fluorescent yellow/green indicates pedestrian crossings and school zones; 
Title: Track day
Content: Yellow. A yellow flag means there is some kind of danger or hazard ahead, so one needs to be extra cautious and vigilant, and must not overtake another driver. ; Red. A red flag means there has been a serious incident and the track day session has been aborted; one must slow down and return to the pits (or where otherwise directed) without overtaking. ; Yellow/Red. A striped yellow and red flag means that either debris has been sighted on the track or that grip is poor, so one must take extra caution. ; Blue. A blue flag means that another vehicle wishes to overtake and one should 
Title: Racing flags
Content: A single waved flag denotes a hazard on the racing surface itself. ; A single stationary flag denotes a hazard near the racing surface. ; Two flags waved simultaneously denotes a hazard that wholly or partly blocks the racing surface (like an accident). This informs the driver that there may be marshals on the track and to prepare to stop, if necessary. The solid yellow flag, or caution flag, universally requires drivers to slow down due to a hazard on the track, typically an accident, a stopped car, debris or light rain. However, the procedures for displaying the yellow flag vary for different racing styles and sanctioning bodies. In Formula 
Title: Yield sign
Content: 1) When the ability to see all potentially conflicting traffic is sufficient to allow a road user traveling at the posted speed, the 85th-percentile speed, or the statutory speed to pass through the intersection or to stop in a reasonably safe manner. ; 2) If controlling a merge-type movement on the entering roadway where acceleration geometry and/or sight distance is not adequate for merging traffic operation. ; 3) The second crossroad of a divided highway, where the median width at the intersection is 30 ft or greater. In this case, a STOP sign may be installed at the entrance to the first roadway of a divided highway, and a YIELD sign may be installed at the entrance to the second roadway. ; 4) 
Title: Road signs in the United Kingdom
Content:  the 30 miles per hour speed restriction (introduced in 1934), with '30' in black letters on a white disc surrounded by a red ring, to indicate it is an order sign. The 30 mph sign was accompanied by its 'derestriction' sign, a white disc with a diagonal black band bisecting it, which marked the end of the restriction. Neither of these signs required separate information plates. The 1934 RTA&R also clarified direction and distance signage, which remained in that form until 1964. All signs were mounted on posts painted in black and white stripes, and their reverse sides were finished black, green, or more 
Title: Yellow line (road marking)
Content:   In Canada, a single broken yellow line is used to separate traffic coming from opposite directions and means that passing is allowed. A single solid yellow line means that passing is allowed but with extreme caution. In the United States, single solid yellow lines are expressly prohibited on two-way undivided roadways by Section 3B.01 of the Manual on Uniform Traffic Control Devices. A single broken yellow line separates opposing traffic and means that passing with care is allowed for traffic in either direction. Section 3B.06 authorizes use of a single solid yellow line in only two contexts: on divided highways (that is, divided by a median strip) to mark the left side of the lane closest to the median (for traffic in both directions), and to mark the left side of the leftmost lane on one-way ramps.
Title: Radar speed sign
Content:  Revision 1, as amended for use in California) Vehicle Speed Feedback Signs Option: A Vehicle Speed Feedback sign that displays to approaching drivers the speed at which they are traveling may be installed in conjunction with a Speed Limit (R2-1) sign. Standard: If a Vehicle Speed Feedback sign displaying approach speeds is installed, the legend shall be YOUR SPEED XX. The numerals displaying the speed shall be white, yellow, yellow-green or amber color on black background. When activated, lights shall be steady-burn conforming to the provisions of CVC Sections 21466 and 21466.5. Vehicle Speed Feedback signs shall not alternatively be operated as variable speed 
Title: Yellow line (road marking)
Content:  A yellow line (solid or dashed) indicates that crossing the line will place a driver in a lane where opposing traffic is coming at the driver. A double yellow line is a painted marking separating two lanes of a road. It consists of two parallel, solid yellow lines, and its presence indicates a two-direction no-passing restriction or no passing zone, where traffic in both directions is strictly prohibited from crossing the line to pass other traffic. Some states, like California, paint a black line down the middle to help drivers see the double yellow line. Where such a marking is present and one vehicle 

Question: what does a yellow 35 mph sign mean?
Answer: advisory speed limits.