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For example at a stop light where multiple cars and trucks are accelerating at the same time all the torque from all the vehicles.

Qmechanic
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dominic weisenburg
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    Scale, scale, scale. Generaously assume $10^{10}$ vehicles averaging $2 \times 10^3,\mathrm{kg}$ each, all heading, say, east and getting up to $50,\mathrm{m/s}$ realtive the ground. What is the resulting change in angular momentum? Now compare to the angular momentum of the Earth (with a mass of $6 \times 10^{24},\mathrm{kg}$ and a surface velocity at the equator of about $460,\mathrm{m/s}$ (the distribution is not uniform so generouslyassume a multiplier of only $1/5$ (compared to $2/5$ for a uniform sphere). How many orders of magnitude difference is there? – dmckee --- ex-moderator kitten Oct 29 '19 at 22:27

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No, there won't be a significant effect, because for every instance of a vehicle accelerating in a given direction there must be a corresponding instance of a vehicle slowing down.

Marco Ocram
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Yes, if there is a net acceleration or deceleration due to traffic, it would effect the rotation of the earth. But the effect would be so infinitesimal as to be unmeasurable.

Hope this helps.

Bob D
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You have to consider that at one point all these vehicles had zero velocity before accelerating so they could decelerate at the stop light. The effect of the acceleration and deceleration would cancel out due to conservation of momentum, so no permanent effect.

Peter
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