Wow, you're right. According to the 1992 schedule, the Pioneer averaged 49mph PDX-DEN, while my schedule averages 45mph. That's a bit less than optimal, but IMHO shouldn't be sacrificed to preserve connections with the CZ in Denver without a four-hour layover there like the Pioneer had.
On the southern segment, however, the average speed does turn out to be 33 mph. I apparently included numerous layovers SB and then forgot to remove them when I changed the schedule.
This schedule gets the north section to 45mph and the south section to 46mph. Some more time could be trimmed out of the schedule, but this is better.
I worked up a schedule for a 'Texas Pioneer' a long time ago that is a little different. You allow too much time between Dallas and Houston. Four or five hours is plenty. Or you could use the former Lone Star route Houston to Fort Worth which was around 6 hours. You are running a bit fast between Denver and Amarillo. I also connected with the CZ in Denver, the Eagle and Heartland Flyer in Ft Worth and sent the HF on up to KC and MSP. In other words everything connected with everything. Here it is if you can read it. I left out all the connecting trains as too complicated to put on here. It's on Word and also Excel if you want all the details. Of course Amtrak has no equipment nor any orders for more so all this is just for fun.
TEXAS PIONEER
Texas Texas
Pioneer Pioneer
lv VANCOUVER BC arr 10:45 PM
7:30 AM lv SEATTLE arr 6:20 PM
11:00 AM arr PORTLAND lv 2:50 PM
11:30 AM lv PORTLAND(PT) arr 1:00 PM
10:55 PM arr BOISE lv 2:40 AM
11:00 PM lv BOISE arr 2:35 AM
1:20 AM arr SHOSHONE(MT) lv 12:40 AM
11:00 PM lv SUN VALLEY arr 3:00 AM
1:00 AM arr SHOSHONE lv 1:00 AM
1:25 AM lv SHOSHONE arr 12:35 AM
3:10 AM arr POCATELLO lv 10:50 PM
12:00 AM lv WEST YELLOWSTONE arr 2:00 AM
3:00 AM arr POCATELLO lv 11:00 PM
3:25 AM lv POCATELLO arr 10:35 PM
6:10 AM arr OGDEN lv 7:50 PM
6:30 AM lv OGDEN arr 7:30 PM
10:20 AM arr GREEN RIVER lv 3:40 PM
10:25 AM lv GREEN RIVER arr 3:35 PM
3:55 PM arr CHEYENNE(BOWIE) lv 10:05 AM
4:00 PM lv CHEYENNE(BOWIE) arr 10:00 AM
6:00 PM arr DENVER lv 8:15 AM
6:45 PM lv DENVER arr 7:30 AM
8:30 PM arr COLORADO SPRINGS lv 5:45 AM
8:45 PM lv COLORADO SPRINGS arr 5:30 AM
10:00 PM lv PUEBLO lv 4:30 AM
6:00 AM arr AMARILLO lv 9:45 PM
6:30 AM lv AMARILLO arr 9:15 PM
1:30 PM arr FT WORTH lv 3:00 PM
2:00 PM lv FT WORTH arr 2:30 PM
3:00 PM arr DALLAS lv 1:30 PM
3:30 PM lv DALLAS arr 1:00 PM
4:10 PM lv WAXAHACHIE lv 12:20 PM
4:40 PM lv CORSICANA lv 11:50 AM
5:11 PM lv TEAGUE lv 11:19 AM
5:58 PM lv N. ZULCH lv 10:31 AM
7:45 PM arr HOUSTON lv 8:45 AM