It is like chess.

On the big ring, to upshift, go up 2 cogs(smaller) and over one(smaller) in front. Like a knight in chess.

From there, a downshift is the opposite, but an upshift is over one, down one, back on the big ring.

A downshift from the big ring is up one over one, as well.

big ring:

up up over = harder gear
up over = easier gear

small ring:
down down over = downshift
down over = upshift

I wonder if I can learn to do that on the road.

Graph 2 - Gear Inches
Ring/Gear 13 15 17 19 21 24 28
52: 105.52 91.45 80.69 72.2 65.32 57.16 48.99
42: 85.23 73.86 65.17 58.31 52.76 46.16 39.57

Sure you can! It is actually easier than it sounds.

Just this past week there was an extensive discussion of such gearing in another thread, but it may have been in the 50+ forum. FWIW, in my experience (which may not count for much) the term Alpine gearing was applied to 2 1/2-step, not 1 1/2-step. That's what Peugeot called it in the catalogs for the 52-36 chainring, 14-26 FW combination on the UO8 in the early 70's.

The term "Alpine" has had several different meanings, which is why I prefer the more precise 1.5-step or 2.5 step.

I use half-step on two bikes, 1.5-step on the other three, and I recommend either configuration, particularly the latter, heartily.

The nice thing about a close-ratio half-step, 1.5-step, or even 2.5-step is that most of your shifts are made using only the rear derailleur, i.e., going up or down two ratio steps at a time as you either work up through the gears while accelerating or down through the gears while climbing. Only when you need to fine-tune do you need to invoke a double shift, which is indeed trivial to learn and to use consistently and accurately in practice.

Here's the drill for a single-ratio change:
Always shift both derailleurs. If you go up in front, you need to go down either 1, for an upshift, or 2, for a downshift, in back. Likewise, if you go down in front, you need to go up by either 2, for an upshift, or 1, for a downshift in back. It's easy, it's fun, and it's eminently practical.

By the way, you can improve your ratiometric progression by using 50-42 or 52-44 instead of 52-42. Alternatively, change sooner from a 2-tooth to a 3-tooth progression in back.

My preferred setups include:
50-42 / 14-16-18-20-23-26
48-40-28 / 12-13-15-17-19-21-24-28
52-42 / 14-16-18-21-24-28 (an old standby, w/ or w/o the 28T cog)
52-42/ 13-15-17-20-23-26

I never really understood 1-1/2 step compared to half step when put to practical use. I think the problem people have with half step, particularly 6/7-speed set ups, is that they tray to progress through the gear range in sequence. In practicality, this is a PIA with all of the double shifts. I find that it is far easier to simply forget which front ring you are in, and progress up and down the cluster/freewheel until you reach cruising speed; THEN adjust up or down a half step if necessary. 1-1/2 step is basically the same, except that you have to climb or dump two in the rear with the double shift. In the end, they are the same concept, and I would encourage you to use which ever you prefer.

This is also why I do not like it for racing/pace lines. You need to work the rear clusters for subtle changes in speed, and only swap chainrings when there is a significant change in terrain (e.g. crests or bottoms of large hills). For this, I prefer true "Alpine" gearing where the front chainrings represent "ranges" with overlap in the gear ratios between them.

Counts for plenty much. You're probably right. I've seen 1.5 referred to as alpine. I'll call it 1.5 step. That clears that up. 52-36 sounds pretty cool. I've also heard alpine described as a huge bail-out gear, so yep, 1.5.

Thanks! You explained it much better than I did. I'll have to practice it some, for sure. My poor straight blocks may wind up retired...