The law against driving under the influence of drugs is being enforced 'inconsistently' by police, according to new figures.
BBC Radio 1 Newsbeat looked at the number of drug-driving arrests since the law changed two years ago, and found that while some forces had made thousands of arrests, others had arrested fewer than 100 drivers for the offence.
In England and Wales, it is against the law to drive with legal or illegal drugs in your body if it impairs your driving. It is also an offence to drive if you have certain levels of illegal drugs in your blood, even if they haven't affected your driving.
After the law was changed in March 2015 to make drug-driving a specific offence, police no longer had to prove motorists who had taken drugs were impaired to drive. Instead, they just had to show that drivers had above a certain limit of certain types of drug -- prescription drugs such as codeine and methadone, as well as illegal substances like cannabis, cocaine and ecstasy -- in their blood.
Newsbeat approached all 43 police forces in England and Wales and asked how many drug-driving arrests they made in the two years after the law changed. Of these, 39 replied with usable data.
To adjust for the fact that some forces are larger than others, the figures were analysed in relation to the total number of officers.
This revealed that around half of the forces made one arrest for every one, two, three or four officers.
Meanwhile, nine forces made one arrest for every 10 or more officers.
The BBC noted that the figures can't be taken as an accurate, like-for-like comparison between forces and don't take into account whether drug-driving is more or less common in different parts of England and Wales.
Zoe Billingham from police watchdog HM Inspectorate of Constabulary (HMIC) agreed that the findings only offer a snapshot into how the law is applied but said the figures suggest there are "major inconsistencies" in the way police forces deal with drug-driving across England and Wales.
"Some forces appear to be proactive in enforcing the drug-driving laws, while others are not," she commented.
"Recognising the vast range of demands on police time, chief constables should look closely at this data and decide whether this important issue of road safety is being prioritised appropriately in their force."
Jason Wakeford, a spokesman for road safety charity Brake, said: "Driving under the influence of drugs is dangerous and totally irresponsible. The law in England and Wales, which campaigners including Brake helped bring about, has gone a long way to help tackle the problem but more needs to be done.
"The Government must make traffic policing a greater national priority, giving the police more resources to deal with drug-driving throughout the year. More approved testing devices are also desperately needed; just two of the drugs listed as illegal under the law -- cannabis and cocaine -- can be tested for at the roadside. An approved kit to detect ecstasy/MDMA should be made a priority."
The Scottish Government has announced plans to introduce new drug-driving laws in 2019, with roadside testing and new limits on driving under the influence of certain drugs.