Time 4 Design
Safety Standards
Public Playground Safety Handbook (US): https://www.cpsc.gov/s3fs-public/325.pdf
Royal Society for the Prevention of Accidents (ROSPA) (UK): https://www.rospa.com/play-safety/advice/en1176-equipment-standard/
Kidssafe (Australia): https://www.kidsafevic.com.au/playground-safety/australian-playground-standards
Drawing Plans
There are many quality drawing plans including those for playgrounds available HERE.
Seesaw plans: http://www.craftsmanspace.com/sites/default/files/free-plans-pdf-files/Seesaw%20playground%20equipment.pdf