A Dead Strip normally used with hand routed tracks and commercial braided tracks. Reed switches are often used in custom routed HO tracks.
Unfortunately, at this time, none of the major track set manufacturers produces a four-lane (or higher) Analog lap counter. You do have options, however. (We will cover the 4 lane options as this is the most popular.) We sold DS lap counting systems, but we dropped this line as it uses a bridge over the track to count the laps, and our club guys found this to be awkward to use. However you may find this at other slot car retailers.
What our club switched to is a PC based system. We use and recommend TrackMate for that, especially in a 4 lane setting! TrackMate uses a Dead strip or REED switch type and includes all the parts you need to get a PC lap counter setup. You need to purchase this directly through the TrackMate website as they do not distribute through retailers.
We have also heard of people customizing two-lane lap counters (such as the one by Carrera). If you are handy, this would be the most economical choice. Unfortunately, we tried to do this for a customer once, and we couldn't figure out how to do it. Only recommend you try this if you are an 'engineer'! Using two two-lane lap counters is not a problem with a road course type layout. Simply insert them in a chicane area designed into your track. Of course this is not possible in an oval-type configuration. In lieu of a lap counter, you can run your races on the honor system where each individual counts their own laps. This method is quite effective when you keep your races short (say 10-12 laps) and if you are running on "crash and burn" race rules, where racers are automatically out of the race when they go off the