[slowmover]

Look forward to reading about the drive.

Yuba City to Sandpoint is about 850-miles which lends itself nicely to an overnight trip.

May I remind the OP that retaining a high average mph relative to the travel set speed will have to do with the choice of stops during the day? Gains can be lost in bad choices. But, how to choose? It’s not quite simple, not if one wants an efficient travel plan. So, how does one define such?

It’s not a matter of fewer stops, per se, but making the necessary ones based on avoiding fatigue (which is safety), and in not losing the MPG margin increases of steady-state driving. A break every two hours of 10-15” is called for, and an hours meal plus fuel at about the days mid-point, or four hours.

Attention to details is the thing. I’m not going to go over the whole route, but a cursory examination shows that Yuba City, CA to Portland, OR though easily 50-miles farther is the same travel time as to Maupin, OR. Terrain is the problem for the shorter route, but traffic volume for the other. I’m going to use IH-5 as an example.

Metro areas are the bugaboo of trip planning. MPG will always be best on an Interstate. And that includes metro areas, unfortunately.

My trip planning for the big truck I drive always involves these sorts of trade-offs: in general, I choose the route that will give higher mpg even if “out of route” per company directions. The trick is in knowing where the OOR doesn’t consume much more fuel (time matters more to what I do) that company dispatch wants to know what I’m doing. I have to explain that it’s the same time at higher fuel mileage or both are better (which is less wear & tear on driver plus truck).

This is the big decision. Time versus distance. As what follows is choosing (so far as possible) the time to get through that metro area. Which itself is a matter of not screwing up my HOS (hours of service) in a significant way; I don’t want this choice to have an effect several days hence.

If I am confronted by the same time on the Interstate to go a greater distance than the US or State Highway, then I know the latter two will involve other than steady-state. It’ll be work. Bad sight lines, too. And unless other truck drivers recommend it (I can have a CB conversation), the longer but easier route will be a better choice. In the big truck.

To get through a metro area and not kill my patiently-added tenths of a MPG is a set of considerations. “Best” time is always just after morning rush hour. Until about 1100. After that, and till 2100 that evening, traffic builds and stays high.

1100 is about when I’d prefer to be at the other end of the metro area. That’s 75-miles from city center in most cases. IH-5 looks as though it’s a string city and built-up quite a few miles to the south.

So, now, to back farther into it, as an early stop to the day is congruent with an early start (daylight driving; no driving after dark), I need a stopping point for the first day of travel that gets me close enough to Portland that I’m at the other end of the metro area as above.

Do you see how this dictates my first day from Yuba City?

We want to just glide along thru the metro areas. Its not about the set speed, or almost not the average. It’s avoidance of braking & accel events to the greatest extent possible.

So now we’re at preservation of average speed through a metro area.

In my Dodge I run 59-mph at 1,725-rpm as my highest fuel economy cruise control set speed on an open highway. Assuming I’m solo (travel trailer at home) this offsets the assertive cruise control on gently rolling terrain (it’s the same mpg as running 62-mph, but cancelling cruise on the rises; I’ve zero interest in non-replicable stunt driving for economy). I might not pass anyone for several days while at this speed. I’m also not having to slow if at all for metro traffic, and I’m sure not accelerating away at their end. Or in and out of a fair number of construction zones.

When we take economy out of the picture and focus strictly on safety (statistically valid practices), the control to speed comes down to traffic volume, thence to vehicle spacing.

Lack of space means an accident sooner or later. Braking to achieve that is contraindicated. And, higher traffic volume means greater spacing problems, even when we distinguish between metro and rural. Town & Country.

Without going off-topic any farther (even as safe driving practice and best mpg track each other) lets posit that a speed below governed trucks — and barely above the 60-mph aerodynamic wall — is about 62-mph. Thus a range of 58-62/mph will cover the problems of spacing in all situations of relative volume and without obstructions.

While 5-mph under the posted limit is for amateurs (one has the sensation of being a rock that water flows around in a stream; ideal), it’s not ideal for MPG, which, again, is about steady state. No deviation in throttle-opening, no use of brakes and dead-minimal use of steering.

We all know that Frank Lees relatives like to run up on each other’s bumpers as metro traffic condenses near city center. And that they jam up again on the other side in accelerating away. So, how to avoid the worst of this even though we’re at a lower speed?

It’s in knowing what lane of travel.

At Portland we’re changing from one Interstate to another. How far out from that exit can we be in the correct lane? (As I don’t know, I’ve had in other cases had to decide on a general rule). Lane One (inside) is nearly always reserved for car traffic (no such thing as fast lane in a metro area to call it a rule), so we can’t use that. And Lane Two is the big truck version of “fast”, so we don’t want that either. Thus, unless Lane Three is the lane to enter and exit, choose it. Till about one mile or greater from the exit. Two miles is better. (If you’ve wanted a manual transmission, this is where it comes into its own: choosing a crawl speed as Frank & Co jam up).

Once last that exit, we are now looking for the point five or more miles past the return to the rural speed limit to come back up to speed and relax. But, why, one asks? Because it will take at least that long for the commercial traffic to sort itself out. True, at 59-mph it may not matter at all (seemingly). But as I’ve above indicated, it’s spacing that matters. Too many chances being taken by too many vehicles at this point.

Spacing: Not less than 100’. That means brakes applied. 200’ is the real minimum and the other vehicle is accelerating away even then. 500-700’ is what’s wanted. A quarter-mile is where one can relax.

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