Ahead of this year's Spanish Grand Prix, the kerbs on the apex of Turns 5 and 7 have been lowered and new concrete verges installed behind them. Additional kerb elements have been installed behind the initial kerbs.
Also, the grass verge on the drivers' left between the exit kerbs of turns 15 and 16 has been replaced by concrete.
As ever, there will be two DRS zones. The first has a detection point 86m before Turn 9 and an activation point 40m after, while the second detection point is at the Safety Car line, with activation 57m after Turn 16.
Tyre compounds this weekend are the same as seen in Bahrain, the C3 being the soft, the C2 the medium and C1 the hardest tyre on offer. These should be well-suited to the high-energy demands and warm weather of the circuit, as the European season gets underway.
While the track was resurfaced last year, which changed its previously bumpy and abrasive nature, the surface has since matured, making it more similar to how it was previously.
Although the teams had a free choice of the 2019 tyre range for pre-season testing, they tended to concentrate on the softer compounds (more commonly used during the year). So they may be missing a bit of data on the hard and the medium.
Barcelona is a good all-round test for the car and tyres, which is why it is so often used for testing, Turn 3 takes the most energy out of the tyres, while the front-left is the most stressed.
Last year, the race was won with a one-stop strategy, the same strategy being used by all the top three. Lewis Hamilton claimed victory for Mercedes after starting on the soft tyre and moving onto the medium. There were also some two-stoppers and three-stoppers.
This year's C1 compound is slightly softer than the 2018 hard, with the C2 being roughly equivalent to the 2018 medium and C3 to the 2018 soft. The selection for this year's Spanish Grand Prix has been made to enable drivers to push hard from the start to the finish of each stint in what are likely to be warm conditions, without resorting to pace management.
The top three teams have all made different tyre nominations, suggesting a varied tactical approach. Ferrari has made the most aggressive selection, choosing more soft tyres, but both their drivers and those of Mercedes have made slightly different selections to their team mates.
Barcelona sits in the middle of the table for the demands placed on the PU, with only 70% of the track taken at full throttle.
The 1km long pit straight stresses the ICE for around 14secs, but its effects are mitigated by only short bursts of throttle round the rest of the 4.655km circuit.
The other period of significant full open throttle comes between Turns 9 and 10, where the ICE is giving its maximum for some 6secs.
Speeds on these two straights will peak at over 300kph with DRS closed, with the maximum speed being just over 325kph on the main straight with DRS open. Ultimate top speed will depend on the wind direction, however.
If there is a head wind, the top speed will be some 1-4kph lower than with a tail wind. Engineers work to offset the negative effect with minute aero adjustments since gear ratios cannot be changed. This nonetheless affects car balance as a compromise needs to be found; a strong tailwind down the main straight is less detrimental than a headwind.
Maintaining good driveability over the lap from the turbo is important as the circuit flows a lot better than the modern tracks visited so far. Turn 3, for instance, is taken almost flat out and the driver needs to be able to carry the speed through the corner.
Turn 10, the 70kph speed hairpin requires good turbo reaction to provide smooth torque delivery and ensure a good exit. Also, traction out of the last corner is arguably more important than top speed to enable an overtaking manoeuvre, which is typically difficult at this circuit.
The undulating nature of the track likewise requires good turbo response. The first sector rises in altitude by some 15m before descending through sector two. Power delivery up the hill needs to be smooth, but likewise sharp on the exit of the corners.
The circuit has a variety of corner speeds and there are good opportunities for the MGU-K to recover energy under braking. The first is the Turn 1 to 3 complex. The cars arrive at over 300kph and brake to 125kph for the first corner.
Another notable chance to recover energy is Turn 5, located in sector 2. The circuit drops downhill, giving the car further momentum, and the driver steps on the brakes for around 3secs. In the T5 braking zone 30% of the braking energy requested on the rear wheels is recovered by the MGUK.
Other braking points come at Turn 10 and Turn 13. T10 is one of the hardest braking zones on the track as the driver will be at 300kph at the entry to the corner. As well as ensuring the MGU-K is recovering as much energy as possible, PU torque accuracy is particularly important here as the circuit goes downhill. Giving the right amount of stability under braking while giving push on the exit is one of the key challenges of the track.
Barcelona is not a particularly challenging circuit for the MGU-H as the pit and back straight will give the MGU-H time to recover the energy lost in the exhaust.
Other short bursts between the turns and high speed corners such as Turns 6 and 9 likewise see the ICE running at partial throttle for extended periods of time.
2019 is the 49th World Championship Spanish Grand Prix, and the 29th to be held at the Circuit de Barcelona-Catalunya in an unbroken run stretching back to 1991.
Michael Schumacher is the most successful driver at the Spanish Grand Prix with six victories beginning in 1995 with Benetton, followed by five victories for Ferrari (1996, 2001, 2002, 2003, 2004).
Of the current grid, only Lewis Hamilton (2014, 2017, 2018) and Kimi Raikkonen (2005, 2008) are repeat winners. The other victors in the field are Sebastian Vettel (2011) and Max Verstappen (2016).
With 12 victories, Ferrari is the most successful team, both at the Spanish Grand Prix overall, and at the Circuit de Barcelona-Catalunya specifically, where it has eight. McLaren has eight victories overall but only four at this venue, while Williams had six of its seven Spanish Grand Prix wins here.
Max Verstappen's 2016 victory was his first in F1. Driving his maiden race for Red Bull, the Dutchman became the youngest grand prix winner at the age of 18 years, 228 days. Verstappen had been elevated to the senior Red Bull team at the expense of Daniil Kvyat, the Russian taking Verstappen's place at Toro Rosso. Kvyat would take the fastest lap of that race - which was also Toro Rosso's first (and, to date, only) fastest lap in Formula One.
Verstappen is one of four drivers to take a debut victory in Spain. Niki Lauda took his debut victory at Jarama in 1974, while Jochen Mass (1975 - Montjuic) and Pastor Maldonado (2012 - Catalunya) recorded their only F1 victories in Spain.
Pole position has been hugely influential at the Circuit de Barcelona-Catalunya. Twenty-one of the 28 races held here have been won from pole. Of the rest, the race has never been won from lower than fifth on the grid, a feat achieved by Fernando Alonso for Ferrari in 2013.
The four drivers making their Spanish Grand Prix debut this weekend all have race experience at the circuit. Alex Albon won the 2016 GP3 sprint race, and was second in 2018's F2 sprint race. Lando Norris finished third in both 2018 F2 races, with George Russell winning the feature. Antonio Giovinazzi is the only one of the four without a podium here. His 2016 GP2 appearance ended with 18th in the feature and a sprint race DNF.
Since their first full season in 1978, this is only the third time that the Williams teams have yet to put a point on the board after the first four races of the season. This also happened in 2011 and 2013. At the other end of the scale, consecutive top ten finishes, Kimi Raikkonen makes this the first time since 2008 that Alfa Romeo/Sauber/BMW Sauber has scored points at each of the first four races of the year.
Check out our Thursday gallery from Barcelona, here.