Why does my Traffic Sign Recognition display of speed limit disappear before I reach next traffic sign

Accelerate while on the "on ramp" until you reach the speed limit + posted on the highway... this way when you reach the highway you will be going the same speed(or close) as the other vehicles ..you can blend in easily.. and NOT cause an accident by going too slow!! On the way down the "on ramp".. start looking at the traffic coming on the highway to find an opening to ease into safely. Use your mirrors and BLINKER... (its easier to slow down a little than speed up)

According to the owners manual

TRAF (Traffic): Press this button to receive traffic announcements. The traffic announcement brackets will appear on the display. TRAF will appear on the display if the current station broadcasts traffic announcements. If the current station does not broadcast traffic announcements, the radio will seek to a station that does. When the radio finds a station that broadcasts traffic announcements, it will stop. If no station is found, NO TRAFFIC will appear on the display. When a traffic announcement comes on the current radio station or a related network station, you will hear it, even if the volume is muted or a compact disc is playing. If the compact disc player was being used, the compact disc will stay in the player and resume play at the point where it stopped. INFO (Information): If the current station has a message, INFO will appear on the display. Press this button to see the message. If the whole message does not appear on the display, parts of the message will appear every three seconds until the message is completed. To see the parts of the message faster than every three seconds, press this button again. A new group of words will appear on the display. Once the complete message has been displayed, INFO will disappear from the display until another new message is received. Hope this helps.

This will sound silly but Diesel engines are very prone to dirty filters, this is the first thing I go to every time

run fault codes and look for failing cam/crank position sensor or loose or faulty wiring to the units.

Just guessing -- don't know what kind of car, engine, etc. but you might want to check the throttle position sensor (TPS) if you have one.

Is dont remember bad, this is the Speed Limit Display. That is a revolutionary new driver assistance system. The Speed Limit Display keeps the driver informed of the maximum permissible speed at all times. A camera fitted near the interior mirror permanently monitors the signs by the road as well as variable speed limit signs on overhead display screens.

If there is a sign indicating a speed limit in the wet, limitations at certain times of the day or restrictions applying only to towing vehicles, the intelligent driver assistance system, part of BMW ConnectedDrive, collects data from the rain sensors, clock and tow bar before displaying the restriction in the cockpit or, if requested, on the Head-Up Display.

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There are several things you can do. Make sure the engine is in good tune, replace the air filter, Air the tires up to 34 pounds air pressure to lessen the rolling resistance, How you drive is most important. Take off from traffic light and stop signs slowly. accelerate steady, don't be in a hurry to reach cruising speed, unless, of course, you are merging with fast traffic. Anticipate stops. Start slowing down sooner when coming to a stop sign or traffic signal. Coast on the downhill streets, and use the cruise control as much as possible. Don't waste gas warming up your vehicle in cold weather. It will warm up quickly while you are driving. Any time spent idling is zero miles per gallon.

this is a sign the engine electric coooling fan is not working.

I have seen these trucks do this from a defective TPS.