select
	speedlocations.hwy,
	speed.speedmph,
	speed.datetime,
	speedlocations.[cross]
from
	speedlocations
	inner join speed
		on speedlocations.id = speed.id
	inner join(	select
				speedlocations.hwy,
				max(speed.datetime) as maxdate,
				speedlocations.[cross]
			from
				speedlocations
				inner join speed
					on speedlocations.id = speed.id
			where
				(speedlocations.city = 'hou')
			group by
				speedlocations.hwy,
				speedlocations.[cross] ) as maxdate_per_hwy_cross
		on speedlocations.hwy = maxdate_per_hwy_cross.hwy
		and speedlocations.[cross] = maxdate_per_hwy_cross.[cross]
		and speed.datetime = maxdate_per_hwy_cross.maxdate