Convoy spacing

.So this


and this

are a thing, and that's evidence for incompetence or lack of discipline.

I've seen spacing ranging from 25 to 200 m between military convoys advised in literature (including field manuals), but typically it's 50 or 100. You need extra spacing between units in addition to this.

The very minimum spacing is the same as in civilian driving; speed multiplied by 1/(2,000 h), such as 40 m at 80 kph (actually it's km/h). This is necessary for avoiding crash accidents when the front vehicle brakes.

A disciplined military can make use of its discipline and avoid many traffic jams by driving steadier than civilians

and this requires some extra distance. So for a fast-moving convoy (80 kph) we're at 50 m spacing minimum, and additional defusing of traffic jams and other troubles by extra spacing between units.

Now let's remember that a 152 mm HE or DPICM shell is dangerous to basic armoured (bulletproofed against normal rifles) vehicles out to 100 m. An airburst HE shell could puncture tires and unprotected diesel fuel tanks at such a distance with a low yet at the receiving end unacceptable probability.

The more vehicles are within such a shell's radius of effect, the worse (obviously). A spacing of 100 m largely negates the effect compared to 50 m. This is also relevant for bombs and Napalm tanks. The risk of secondary effects jumping over from vehicle to vehicle (one explosion or burn triggering the next) through much of the convoy is largely negated with spacings of 50+ m.

The direct damaging effects aren't the only issue with HE munitions, though. WW2 shells created craters of this size (at least when delay fuses were used):

and today's commonly-used 152 mm HE shells have much more explosive power.

One such shell hit on a road and the convoy would come to a halt. All wheel drive military vehicles would likely be able to bypass it on many roads, but not necessarily without some prior effort (digging, cutting trees, removing signposts, filling up a parallel drainage channel in some places). There's almost never a bridgelaying vehicle at hand to instantly bridge the crater and the situation is about the same with excavators and dumpers that could quickly fill the crater.

So the competent way to deal with such an obstacle is to immediately signal the entire convoy (minimum the march unit leaders) by radio to stop. This maintains the spacing and thus the reduced lethality of attacks by mortar, artillery or air (it's not helpful against infantry ground attack and thus not something you need in stupid occupation wars).

The alternative is a bunching up of the convoy, and it becomes an easy target. The soldiers might be tempted to leave their vehicles to bunch up and chat, and might miss radio calls of their cab-installed radio. Bunched-up convoys might even begin to block the road entirely (see previous link).

Another competent response it to immediately initiate the obstacle removal (trees felled by explosive charge to cover a road qualify as well, not every obstacle is a crater) or prepare and initiate the bypassing. Medical, wrecker, excavator vehicles might need to bypass the waiting vehicles on the road and military police should also be able to move freely (one good reason for giving them motorcycles, or at most narrow 4x4 cars).

The ease of bypassing is important for the choice of routes (roads through forests are a terrible, but often the least terrible, choice) and is the reason why the heavy logistics vehicles meant for hauling diesel and artillery/mortar/tank main gun munitions at battalion to corps level should have all-wheel drive (8x8, 10x10) and shouldn't be semi-trailers. Civilian-style motor vehicles can haul supply from depot (or fuel storage) to some corps supply hub, where the military all wheel drive vehicles can pick the supplies up.

Their limited offroad abilities are not crucial for driving over agricultural fields or through nature's reserves; they're crucial for being able to hide offroad, for better performance on wet unpaved roads and for being able to bypass obstacles.

- - - - -

One more thing; I don't understand why a proven technical solution to nighttime driving has fallen out of favour, partially being replaced by primitive and much less effective alternatives: I'm thinking of the Notek lights. They were designed to work at a specific distance, which was fine for certain speeds. Note lights cost almost nothing and should be installed on all military vehicles for use in the field other than motorcycles in my opinion.


So this Notek system had four taillights in a box, spaced a bit. At distances of 35...200 m the human eye saw only one light, so the driver know he had fallen behind. At 25...35 m the following driver saw two lights and knew his distance was fine (for the cruise speeds of WW2). He saw all four lights when he was too close, at less than 25 m. We could easily adapt this for higher cruise speeds of today by making the spaces a bit wider and the (green) lights brighter. The costs would be negligible. We could maintain an acceptable spacing even during nighttime road marches. Instead, today's planners would rather think of installing mil spec infrared driving aid vision systems and then nobody would train the drivers to make good use of them to maintain the correct spacing.

Enemy air power doesn't require the visual spectrum; it can use radar and infrared. Light discipline is still helpful to reduce the threat of stragglers ad other poorly equipped ground threats and it makes traffic reconnaissance and dumb munitions bombing runs much more demanding.





  1. One main reason for many such things you see now in the ukraine is the mud-period, the rasputiza, which has started parallel to the invasion. There are many vids which show russian vehicles offroad stuck in mud, even main battle tanks and other such vehices with chains.

    And on the streets there is simply not enough space to hold the mentioned spacings, otherwise the overall length would be to long.

    Also with some few exceptions the ukraine airforce is down and the russian artillery wins actually the artillery battle, so the risk is not as high as you might think here.

    1. The simple solution is to not send more formations to march on a road than the road has capacity. This is a corps-level or higher fuck up, not the nature's work.

      Germany had the same kind of epic traffic jam in the Ardennes May 1940. The difference is hardly any Belgians fought in the Ardennes, while the Ukrainians apparently fought a delaying action from the border to Kyiv.

  2. Read once an AAR about another epic traffic jam in the invasion of Yugoslavia before the left turn into Greece. IIRC besides all sorts of issues and breakdowns most of it was due to trying extra hard to push man and material over the pass. Exceeding the capacity by trying to get through fast made progress slow.

    Might be partly so in Ukraine as according to Twitter most of the Russian forces are engaged now.

    Letting engines run, stop and go between crawl must drive fuel consumption through the roof. With lots of fuel getting blown up the advancing forces might find themselves in a bad spot.

    How will they manage to supply themselves? Are there Ukrainians lying in the woods? Drops seem risky so close to the capital. Maybe this is why the Russians have been sending ILs in this direction...

    Overall it doesn't seem unlikely that the big convoy will mostly run out of fuel.


    P.S: Was it the first big modern mass migration with so many cars? Sadly that also caused a brutal jam with lengths over a 10 km

  3. If the Russians were truly concerned about NATO intervention- as Putin's recent escalation re: nuclear forces suggests - then they would hardly be presenting NATO with such a juicy target as a 60km long badly-spaced convoy.