I have had some experience with both "observing" at the sun tunnels and driving the old Central Pacific RR grade, which was eventually abandoned after construction of the Lucin Cutoff. On December 21, 1991 I went to the tunnels with VonDel Chamberlain. It was particularly interesting because there was a partial lunar eclipse the night of the 20th/21st, so the Moon was also aligned in the opposite pair of tunnels, both at sunset and sunrise. I've got pics of the event buried in a moving box - somewhere. It was a bitter cold night, at least -20F, and the only other people nuts enough to be there were some dumb college kids without warm clothing who arrived pre-dawn for the sunrise. Still, I enjoyed the experience. I also went there with the family the following June for the solstice. There were a few more people there in June. ;-) The Lucin Cutoff (the old Great Salt Lake trestle) was built because by about 1900 it had actually become cheaper than continuing to run trains over Promontory Summit. By around 1940 the rails had been removed from the UP and CP grades, roughly between Odgen and Lucin - hence, the "Lucin Cutoff". The Central Pacific grade is now maintained by the BLM and is supposedly drivable, except for bypasses at all of the wooden trestles. I've tried driving the CP grade between Lucin and Promontory on three occasions, and each time I've ripped open a tire on old RR spikes still buried in the soil on the grade. Finally, I determined one year to do the whole thing by bicycle. My plan was to stay on the grade as much as possible, even across the wooden trestles. I left Promontory in the morning one day in October and pedaled to Lucin, then from there to Montello where my wife met me, a total of about 120 miles. It took three days and about 15 liters of water, that I carried on my bike all the way, until I ran out. I saw no one else the entire trip until I was well past Lucin headed to Montello off-grade. The second night I camped at the cemetery at Terrace, but I neither saw nor heard any of the ghost trains that have been reported in the area. I only had to leave the grade once or twice to bypass missing trestles, otherwise I was able to bicycle the whole thing, even on the wooden trestles that are blocked to car traffic. It was one of the best trips to which I've ever treated myself. Fascinating history and desert scenery. Well worth the time and effort, but my joints all suffered for a few weeks afterward. Guess I'm getting old(er). Kim