The odd-even rule that restricts the use of private vehicles on Delhi's roads - an attempt to combat the deadly pollution shrouding the capital - kicked in this morning. Chief Minister Arvind Kejriwal said 15 lakh vehicles will be off Delhi's roads today. Pollution levels in the city dropped marginally in morning due to a slight increase in wind speed, but the air quality remained in the ''severe'' category. A public emergency was declared in Delhi on Friday after the pollution levels entered into the "emergency" category for the first time since January. On Sunday, pollution levels peaked to a three-year high that made breathing difficult and lowered visibility that affected road and air traffic.