There have been some major rule changes announced for 2007. These are as follows and have been compacted for easier understanding:

Engines
All engines that were used by teams in the last two races of 2006 and homologated must be used for the upcoming season and for the seasons between 2008 and 2010. This decision has been taken with a view to cut down development costs and has come to be known as an ‘engine freeze’. During this period, though, some minor development under the control of the FIA would be allowed.

The two-race engine rule will no longer apply to Friday practice sessions. This means any driver starting a meeting with a fresh engine will not be penalised for an early failure. It also means drivers may opt to use alternative engines on Fridays and save their race engines for the remainder of the weekend.

Tyres
With Bridgestone becoming Formula One racing's sole supplier for 2007, each team will receive only two specifications of tyre per event.

However, they will stand to get more sets - four per driver on the Friday and ten for the remainder of the weekend. Each driver must use both specifications during the race.

Safety car
In 2007, safety car regulations have been modified to prevent drivers diving for the pits the minute the safety car comes onto the circuit, and to stop backmarkers interfering with the leaders during a race restart. No car is allowed to enter the pits until the field is bunched up behind the safety car and before the safety car returns to the pit any lapped car running between cars on the lead lap must overtake those cars and the safety car before taking up their correct position at the back.

Friday Practice
In a slight change to the Grand Prix weekend format, Friday's two practice sessions have been extended from 60 to 90 minutes each.

Third cars will no longer be allowed, but all teams are now permitted to run one alternative test driver in each Friday session. The alternative driver must be nominated beforehand and may use either of the team's race cars.

Safety
A GPS marshalling system, involving a cockpit light display of flag signals in each driver's car, is being introduced. This will allow Race Control to alert drivers to potential hazards more effectively.

All cars must also now be fitted with a medical warning light just ahead of the driver's cockpit. This is to provide rescue crews with an immediate indication of the severity of the accident and is connected to the FIA data logger.

The crash tests that Formula One cars must pass have been made more stringent. The velocity used in the frontal impact test has been increased from 14m/s to 15m/s, while the minimum size for the impact-absorbing structure has also been raised. In addition, the driver’s cockpit must now be clad in special anti-penetration panels made of Zylon. An additional five kilograms has been added to the car’s minimum weight requirement to offset the weight of the panels.

Courtesy: formula1.com