In an attempt to cut costs, since 2006 new regulations required mechanical front and rear differentials, while the central differential remained active. Active suspension and water injections were also prohibited. Cars entered by a manufacturer had to be equipped with the same engine for two rallies; further limitations were imposed on the changing of some parts, including suspension, steering, turbochargers and gearboxes.
Pacenotes are a unique and major tool in modern rallying. Television spectators will occasionally notice the voice of a co-driver in mid-race reading the pacenotes over the car's internal intercom. These pacenotes provide a detailed description of the course and allow the driver to predict conditions ahead and prepare for various course conditions such as turns and jumps.
Road rallies are the original form, held on highways open to normal traffic, where the emphasis is not on outright speed but on accurate timekeeping and navigation and on vehicle reliability, often on difficult roads and over long distances. They are now primarily amateur events. There are several types of road rallies testing accuracy, navigation or problem solving. Some common types are: Regularity rally or a Time-Speed-Distance rally (also TSD rally, testing ability to stay on track and on time), others are Monte-Carlo styles (Monte Carlo, Pan Am, Pan Carlo, Continental) rally (testing navigation and timing), and various Gimmick rally types (testing logic and observation).
To limit power, all forced induction cars were fitted with a 34 mm diameter air restrictor before the turbocharger inlet, limiting the air flow to about 10 cubic meters per minute. The restriction was intended to limit power output to 300 hp although some WRC engines were believed to produce around 330–340 hp. Engine development did not focus on peak power output but towards producing a very wide powerband (or power curve). Typically, power output in excess of 300 hp was available from 3000 rpm to the 7500 rpm maximum, with a peak of 330–340 hp at around 5500 rpm. At 2000 rpm (the engine idle speed in "stage" mode) power output was slightly above 200 hp.
1968 brought the first of a series of British-organised intercontinental rallies, the Daily Express London-Sydney Marathon, which attracted over 100 crews including a number of works teams and top drivers; it was won by the Hillman Hunter of Andrew Cowan/Brian Coyle/Colin Malkin. Not to be outdone, the rival Daily Mirror sponsored in 1970 the London-Mexico World Cup Rally, linking the stadia of two successive football World Cups, on a route that crossed Europe to Bulgaria and back before shipping out from Lisbon to Rio de Janeiro, after looping around South America, and a run through some of the most frightening sections of Peru's road race, the Caminos del Inca, they wrap it up being shipped to Panama and a final run up Central America. The Ford Escort of Hannu Mikkola and Gunnar Palm won. These were followed in 1974 by the London-Sahara-Munich World Cup Rally, and in 1977 by the Singapore Airlines London-Sydney Rally.