1) Its not about the speed, its how long you last :The rider in Lane splitter does a wheelie and speeds up when you touch the screen, which makes the accelerometer steering a lot harder to control. Focus on surviving as long as you can before speeding up on the traffic. This is a rookie mistake every beginner makes.
2) Use Power Ups Wisely:Magnets and helmets should help you get almost double what points you score and what coins you collect. Once you have a good hold of controlling your vehicle, these power ups should pay for themselves to the point where you don't need to think twice before using these upgrades.
3) Don't buy donuts, Instead level-up upgrades :Its quite easy to lose the cops. Just speed up carefully and you should lose him soon, which is why the donut power up is nearly useless. Leveling up magnets and and any other future power ups that will be released in the future will come in handy though.
4) Open your eyes, read the signs:Don't miss those money bags that hang on the side of the car. And be careful when the screen flashes "traffic ahead". Speeding up with doing a wheelie makes you lose sight of these quick sign flashes. So look out for these to survive longer and achieve a better score.
Last but not the least have fun. Lane splitter like doodle jump, temple run and tiny wings is all about practice. You will get better at it eventually. I went from few thousands to nearly 40,000+ in a couple of weeks.