If you are transporting hay or straw it is important that it is secured correctly. It’s an offence to deposit hay and straw onto the highway to such an extent as to cause a hazard. You must also ensure that that the load is not likely to cause a danger or a nuisance to any person or property by way of it falling or being blown from the vehicle.
When transporting bales you must make sure that there is adequate strapping to ensure that the load does not move. You should use straps both across the load, and across the length of the load. This is to help ensure that there is no movement sideways, forwards or backwards.
You should ensure that the vehicle is roadworthy. This includes making sure your trailer brakes are well adjusted, and ensuring tyre pressures are even and suitable for road use. The NFU produce the Farm Vehicle Health Check scheme to assist you with undertaking safety checks, it can be found here.
If there is a risk of hay or straw blowing off the load, you should consider using netting or sheeting to cover the load.
For further information, the Department of Transport produce a Code of Practice on Safety of Loads on Vehicles. It can be found here