Interesting - that must be country specific!
I agree with respect to minimising gear changes but there is also a strong incentive to conserve momentum, ie avoid braking, that will compromise the 'safe' distance?
In the UK at least the concept of trucks driving even a truck length apart is subjectively rare and at busy times multiple trucks driving ~4-5m apart are common, especially where the lead vehicle has not reached 60mph.
(In the UK trucks are limited to 60mph/97kph, these speeds usually being exceeded on downhill stretches. )
Any UK car driver will have experience of a truck driving ridiculously close behind them - far less safe given the relative stopping distances.
Cheers
Div
-------- Original Message --------
On 7 Sep 2021, 11:45, François Vaudrin < francois.vaudrin.1@xxxxxxxxx> wrote:
Danke Jakob,
It's perfect, I'll think about what I can do with the "tau".
If it can help for future improvement of SUMO, here's some additional information that I received:
- The braking distance is different if the truck is full or empty.
- The delay for the truck to start braking would be approximately 3 seconds for a semi-trailer: 1 second for the reaction time + 2 seconds for the mechanical delay to reach the rear of the
truck (to apply the brakes).
- Truckers try as much as possible to keep a constant speed to avoid frequent gear changes and they try to keep a gap in order to avoid frequent stops and departures.
Best
De : sumo-user <sumo-user-bounces@xxxxxxxxxxx> de la part de Jakob Erdmann <namdre.sumo@xxxxxxxxx>
Envoyé : mardi 7 septembre 2021 02:13
À : Sumo project User discussions <sumo-user@xxxxxxxxxxx>
Objet : Re: [sumo-user] Safe distance for a trucker (headway)
I'd guess that in this rule of thumb, truck length is a proxy for weight and hence deceleration capability.
Since the relationship between decel, speed and headway isn't linear in speed, you'll find it easier to reproduce the linear rule-of-thumb gaps with different values of tau for different lengths of truck.
Though, when following the physics, modeling it with different values of decel for different sizes of truck should be a better fit for reality.
Per my understanding the trucker rule is just an easy-to-calculate approximation for the physics.
Hello,
It seems the rule for truckers is to keep a safe distance of one truck length per 10 km/h. So, if a truck driver is traveling at 100 km/h and his truck is 20 m long, he should keep a distance of 200 m from the vehicle in front of him.
I thought to use the "tau" parameter, but it
is related to reaction time as I understand and it does not seem to
take into account the length of the truck.
Thank you,
François Vaudrin, PhD
CANADA
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