What is the main factor determining the grip of a bus's tyres on a dry road?

Grip is the force of friction created at the point of contact between the tyre and the carriageway. Different types of surfaces, such as asphalt, concrete or block paving, have different properties, which has a direct impact on the value of this force. Therefore, even on a dry road, the type of material from which the surface is made fundamentally determines the vehicle's grip.