I'm on dialup, so I occasionally do just that, ask other racers.
There is what looks like a music equalizer band down in the lower left corner of the screen. This is the latency meter (for lack of a better term, or it could really be called that ). Your bar is the green one. It will move up if you get too much lag, eventually to the point where you start to see red. Sometimes you will see all the bars moving up. Usually this indicates that someone else is about to time out. They move up also (all together) sometimes when a new guest is joining the server.
If you are in the heat of a battle and see a single car jumping around or say (3.21S) above where you last saw them, that particular racer is lagging. If you see ALL cars disappear, then more than likely you are lagging.
Since March of 05 . Works great. Rarely lag or disconnect unless I try to grab a skin or two while on the server. Usually do a skin grabbing from the replay session every now and then.
Bottom of the screen, you will see a series of Red Bars. One of these bars will be Green ( your connection ) The higher the bar, the more latency you have. The longer the bar stays up, the more stutter you will have while racing online.
How to stop it, now thats opening up a can of worms. Could be your PC, Firewall, AV Software, your connection, your ISP, your ISP's connection, your modem, your cable from pc to modem, depends on what router you connection to at your ISP, and whether your Exchange ( BT Box ) is upto scratch.
Do some speed tests to see if its your internet connection, or just LFS. If you have ADSL, http://www.adslguide.org.
shift F8, and then look at different players.
If they all have a ping of 250+, chances are that YOU have a ping of 200 to all of them, because most of them will have a ping around 50.
See my post above yours. But it doesnt work on all views, nor when the player has already finished.
Maybe there's another option that I'm not aware of...